Back in the day, Bandai had its own Japan exclusive portable console: the Wonderswan. That meant that if you liked Digimon in the west then you had very few available options. However, some titles did make their way across to more accessible systems such as the Gameboy Advance. This is one of them and, as a result, I ended up playing this a lot as a kid.
Digimon Battle Spirit is what you would call a party or platform fighting game. Characters have limited move pools due to the control limitations and instead of a health bar they drop small orbs when hit. Whoever collects the most orbs from the opponent after 2 minutes is declared the winner. Also, Calumon shows up twice per match and whoever catches it digievolves which means they become invincible, gain new attacks and deal a ton of damage for a few seconds.
The main game mode is a campaign consisting of 7 fights and a final boss. Beat the game with each character to unlock more fighters... that's it really. It's not a deep game at all, but it's fun.
In a different note, I really like the presentation. The chibi art style is really cute and the music is nice to listen to, although it doesn't have much to do with the show. Most of the characters you would want to play as are present too... and Sukamon, for some reason.
To conclude, this game is alright. I'm kind of biased because I like Digimon, especially Tamers, so I wouldn't really recommend it for people who are unaware or don't like the series.