What a lovely Undertale-styled RPG! This is definitely one of the most unique jam games I've played thus far, you did a good job on this! The gameplay was interesting, the Gayzing mechanic was satisfying to pull off, and the dialogue/writing is a nice combination of cheesy and serious - not too memetic to not be taken seriously but not too dramatic to be unnecessarily edgy either. I definitely can tell where the story was going from the beginning but things still unfolded smoothly.
First of all, a few bugs:
+ It is possible to have a save file corrupted when loading it. I already reported it in the Touhou Game Dev server, but I'll add a few more details I missed since I think this may partly be my fault: I saved, exited and reloaded the game, and then pressed Start instead of Load accidentally. I immediately closed the game after pressing it in an attempt to preserve my save, but I believe this action is responsible xd... I think having multiple save files or a "You already have a save file" warning when starting a new game with one would work.
+ There are some small bugs such as being able to start a battle twice (the battle jingle and enemy appears twice) or start a battle while talking to someone else (for example, a fairy was right next to Cirno and I entered battle as I initiated a conversation with her). These are not game-breaking and stop when you clear the battle/leave the area, but it's worth taking a look at.
Now, as a danmaku/bullet hell shmup player I do have comments and complaints to say about the Undertale gameplay of the game:
+ I like the dynamic enemy design - as in, it isn't just "enemies have more HP and harder patterns". Some enemies in the latter area have difficult patterns but less HP to compensate, and I think it's a pretty nice touch.
+ The bosses are overall decent and solid, there's a clear phase progression to each of them and I enjoyed the variety of patterns they have. I don't think said patterns mesh too well with each other though, it feels like they're just doing their own thing and not working together. A good way to fix this would be making the two bosses' bullets interact with/rely on each other - for example, Mike's coins following Nazrin's rats instead of you, or the stars coming from Alice's dolls instead of being shot by Marisa. The final boss is... well, I'll leave a full section for it.
+ I'm not sure how to feel about focus and shot being tied to one button? Since part of the gameplay involves having to break the enemies' barrier under a time limit (said time limit here being how long the pattern lasts), it doesn't make sense that you have to stop shooting to make tricky dodges and risk dealing little to no damage in the next turn. Barriers are pretty weak at least so it helps.
+ Speaking of barriers... I don't think there's any use for the green rectangular barriers in later areas' enemies? They take forever to take down and you may as well just focus all shots on the big shield, and I dunno if they actually affect Sakuya's damage anyway.
+ Bullet hitboxes, specifically that of the bigger ones, are off. Meiling's hitbox and small bullet hitboxes are accurate for the most part, but some larger bullets have hitboxes bigger than their sprite (see: the generic orange balls). It makes dodging dense patterns way harder than it should be...
+ Now... the final boss. It has cool concepts but is overall a big unbalanced mess, which I'll chalk it up to jam time constraints. First of all, I think the telegraphs are honestly kinda bad for two of the attacks: the lasers and the crosses that fall from above. Delay lasers last very short and are very hard to see (this was also an issue for MariAli's laser attacks), and the crosses just don't have any warning lasers at all (which is a problem since they fall fast and aren't very big!). Plus, the "patterns not working together" issue is extremely present here. Finally, the second phase looks cool and I appreciate you being invincible during it, but it's just absolutely borked.
Sorry if this all sounds too critical! I really had fun with the game and I hope you can take my criticisms into heart to make even greater games!