I had heard this game was a pretty heavy game with a weird whimsy to how it handles things, and that's pretty close to the truth. LISA is like if Mad Max were a JRPG with an Earthbound-like whimsy to it. It's a really fun, albeit a little unconventional, JRPG that I enjoyed a lot ^w^. I beat it twice. Once on normal mode with the "Joyful" ending, and then again on Pain Mode. The first time through took me about 13 hours, and the 2nd took me about 7 hours.
Pain mode can be activated (a bit too easily, imo) by picking a choice at the beginning of the game, but it's not exactly hard mode. It just adds a couple extra (and not very hard) mini-bosses as well as making each save point only usable once. It adds an interesting level of planning to the game as well as challenge of just "don't die, lol", but it honestly doesn't change the overall game enough to realllly warrant it for most people, and the 1-use save points make it too hard to make it really recommendable to ever do on your first playthrough.
The story of LISA has you in the shoes of Brad, a man living in the post-apocalyptic land of Olathe after some catastrophe has led to the disappearance of all women and a society of only men dreading their eventual extinction. Fates change when Brad happens upon an infant lying in a field, and upon bringing it back to his camp of friends discovers that it is indeed a baby girl. Brad decides to raise the child as his own adopted daughter, as his friends help keep her a secret living in a cave below their tent. Years pass as she grows into adolescence in total secret. Then one day, Brad returns to see that his friends have been murdered and the girl has been stolen away, and Brad sets off on a mission of revenge to get her back. This is an extreme simplification of these events, but LISA's story takes a series of turns that get the story to a pretty dark place. I'm not quite sure I'd compare it to Undertale (not just because Undertale came out nearly a year later), as the path of the story is linear and doesn't have that level of choice-making, but by the end of the game you will certainly begin to question whether Brad is/has been doing the right thing. I'm leaving it really vague as to not to spoil, but I personally really enjoyed the story and how it deals with themes of 'what it really means to sacrifice for someone else' as well as 'when justice becomes injustice.' I do feel it's worth specifying very clearly, though, that LISA deals implicitly and/or explicitly with themes of violence, emotional/sexual abuse, and sexual violence, so if those aren't the kinds of things you can handle, playing through LISA is probably not a good choice for you.
The gameplay is fairly standard JRPG, but not that typical in some ways. The game has very few areas where you could actually grind for EXP. Most enemies you fight are single-battle enemies or mini-bosses who die when you beat them, so you can't re-fight them. There are some fields of snakes or trash men at certain points, as well as a wrestling ring you can get to later that you can use to grind for EXP, but they're the exception rather than the rule. Random battles are not something LISA has many of.
There are a TON, like 25, playable party members, all with fairly varying styles of how they play. Brad, for instance, is one of few characters who can use combos of the WASD keys to both do 5 regular attacks, or chain them together to activate one of his special moves (a very tiny bit like Sabin in FF6, but your D-pad inputs do damage as well in addition to the moves taking from a mana pool). There are a few more standard spell-users, a couple more combo-users, but you also have characters who need TP (which is basically a "rage" mechanic) where they get MP by both taking damage and dealing damage with their normal attacks. Out of the 25, there are some team compositions that are better than others, of course, but there are very few party members who are straight-up awful. Members who are very powerful often aren't very flexible, and vice-versa. And those who are fairly powerful and flexible strategically are often addicts and that's something else entirely.
Brad is a recovering drug addict from the drug Joy (and if you don't take any or give any to other party members, you get a secret ending on normal mode). Several party members come already addicted to Joy, and if they don't take it they go through withdrawal. Taking a Joy gets you the Joyful status effect which makes all your hits crits for like 1-5 turns (which can be very powerful on a character like Brad who effectively can get 4-5 standard attacks + a special move off all in one round). Being in withdrawal basically sets your attack power to 0 as well as tanking your speed, defense, and max HP, so it REALLY sucks. Your special attack doesn't decrease though, so you can still do special moves to hurt stuff, but it's nothing like not being in withdrawal. You can either get out of withdrawal by taking Joy, of which you cannot buy and have a very limited supply of the stuff you can find (there is a hard limit in the game of the stuff, so you NEED to conserve), or go through however many turns of combat (usually around 10, but it could be way less or even more than that) and it will eventually go away until it comes back again sometime while you're wandering the overworld. Addiction adds a whole new level to how you strategize the boss fights, but the game is very beatable without it if you find a team that works for you. (I personally really liked using Nern, Fly, and then either Jack or Carp).
One of the last things I'll mention is that there are SO many party members (all but 3 of which are optional and need to be hunted down, and most of them aren't too hard to find) is that there are some things that will permanently kill party members. Mostly it's story choices or optional bosses, but how because them permanantly dying IS a thing that can happen, that's why something like Pain Mode with limited saves would be so ill advised on your first runthrough. Because EXP grinding isn't easy to do to grind up a new character, losing a team-mate REALLY sucks if you aren't expecting it, so save-scumming is something that is basically mandatory to conserve your sanity XD
Verdict: Highly Recommended. LISA is a fantastic JRPG that is pretty far off the beaten path as far as a typical narrative or mechanics go. I even didn't mind immediately replaying through a fairly long game because the character variety is so great and the world is just so cool. This is a great game totally worth picking up if you want something to make you think a bit but not too far from the mechanics you're familiar with in a JRPG.
Pain mode can be activated (a bit too easily, imo) by picking a choice at the beginning of the game, but it's not exactly hard mode. It just adds a couple extra (and not very hard) mini-bosses as well as making each save point only usable once. It adds an interesting level of planning to the game as well as challenge of just "don't die, lol", but it honestly doesn't change the overall game enough to realllly warrant it for most people, and the 1-use save points make it too hard to make it really recommendable to ever do on your first playthrough.
The story of LISA has you in the shoes of Brad, a man living in the post-apocalyptic land of Olathe after some catastrophe has led to the disappearance of all women and a society of only men dreading their eventual extinction. Fates change when Brad happens upon an infant lying in a field, and upon bringing it back to his camp of friends discovers that it is indeed a baby girl. Brad decides to raise the child as his own adopted daughter, as his friends help keep her a secret living in a cave below their tent. Years pass as she grows into adolescence in total secret. Then one day, Brad returns to see that his friends have been murdered and the girl has been stolen away, and Brad sets off on a mission of revenge to get her back. This is an extreme simplification of these events, but LISA's story takes a series of turns that get the story to a pretty dark place. I'm not quite sure I'd compare it to Undertale (not just because Undertale came out nearly a year later), as the path of the story is linear and doesn't have that level of choice-making, but by the end of the game you will certainly begin to question whether Brad is/has been doing the right thing. I'm leaving it really vague as to not to spoil, but I personally really enjoyed the story and how it deals with themes of 'what it really means to sacrifice for someone else' as well as 'when justice becomes injustice.' I do feel it's worth specifying very clearly, though, that LISA deals implicitly and/or explicitly with themes of violence, emotional/sexual abuse, and sexual violence, so if those aren't the kinds of things you can handle, playing through LISA is probably not a good choice for you.
The gameplay is fairly standard JRPG, but not that typical in some ways. The game has very few areas where you could actually grind for EXP. Most enemies you fight are single-battle enemies or mini-bosses who die when you beat them, so you can't re-fight them. There are some fields of snakes or trash men at certain points, as well as a wrestling ring you can get to later that you can use to grind for EXP, but they're the exception rather than the rule. Random battles are not something LISA has many of.
There are a TON, like 25, playable party members, all with fairly varying styles of how they play. Brad, for instance, is one of few characters who can use combos of the WASD keys to both do 5 regular attacks, or chain them together to activate one of his special moves (a very tiny bit like Sabin in FF6, but your D-pad inputs do damage as well in addition to the moves taking from a mana pool). There are a few more standard spell-users, a couple more combo-users, but you also have characters who need TP (which is basically a "rage" mechanic) where they get MP by both taking damage and dealing damage with their normal attacks. Out of the 25, there are some team compositions that are better than others, of course, but there are very few party members who are straight-up awful. Members who are very powerful often aren't very flexible, and vice-versa. And those who are fairly powerful and flexible strategically are often addicts and that's something else entirely.
Brad is a recovering drug addict from the drug Joy (and if you don't take any or give any to other party members, you get a secret ending on normal mode). Several party members come already addicted to Joy, and if they don't take it they go through withdrawal. Taking a Joy gets you the Joyful status effect which makes all your hits crits for like 1-5 turns (which can be very powerful on a character like Brad who effectively can get 4-5 standard attacks + a special move off all in one round). Being in withdrawal basically sets your attack power to 0 as well as tanking your speed, defense, and max HP, so it REALLY sucks. Your special attack doesn't decrease though, so you can still do special moves to hurt stuff, but it's nothing like not being in withdrawal. You can either get out of withdrawal by taking Joy, of which you cannot buy and have a very limited supply of the stuff you can find (there is a hard limit in the game of the stuff, so you NEED to conserve), or go through however many turns of combat (usually around 10, but it could be way less or even more than that) and it will eventually go away until it comes back again sometime while you're wandering the overworld. Addiction adds a whole new level to how you strategize the boss fights, but the game is very beatable without it if you find a team that works for you. (I personally really liked using Nern, Fly, and then either Jack or Carp).
One of the last things I'll mention is that there are SO many party members (all but 3 of which are optional and need to be hunted down, and most of them aren't too hard to find) is that there are some things that will permanently kill party members. Mostly it's story choices or optional bosses, but how because them permanantly dying IS a thing that can happen, that's why something like Pain Mode with limited saves would be so ill advised on your first runthrough. Because EXP grinding isn't easy to do to grind up a new character, losing a team-mate REALLY sucks if you aren't expecting it, so save-scumming is something that is basically mandatory to conserve your sanity XD
Verdict: Highly Recommended. LISA is a fantastic JRPG that is pretty far off the beaten path as far as a typical narrative or mechanics go. I even didn't mind immediately replaying through a fairly long game because the character variety is so great and the world is just so cool. This is a great game totally worth picking up if you want something to make you think a bit but not too far from the mechanics you're familiar with in a JRPG.