Sid Story is the most unique gacha game I've played so far. In all honesty it's almost more accurate to call it a "card-collector" rather than a game, as the combat system almost feels like an afterthought.
Sid Story's combat system is similar to most gacha games, in that you assemble a team of three monsters ("Sidians", or "Sids" for short). Once combat begins, the player has no input into the outcome; the Sids attack and use their special abilities automatically. If they win, you get the usual rewards. If they lose, you can have another go at the enemy immediately and the enemy monster doesn't regenerate its health. That's right; your Sida instantly regen all health and abilities while the enemy monster doesn't. Effectively, this means that there is never a monster that can't be beaten; you just have to throw your Sida at it enough times.
So why play Sid Story if the combat is so shallow? The are on the cards is exceptional. It is, of course, heavy on the T&A; it's a Japanese game and this is how Japanese games look. But the art itself is very high quality. As you level up your Sids, their cards change aesthetically and get even better-looking.
There is a narrative that plays out as you make your way through the game, which is silly and self-aware and provides a few chuckles.
Overall, Sid Story is fun and doesn't require a lot of thought to play. If you're a fan of anime art, give it a go.