Reminds me of Project Touhou. I like that you've made their weapons into spaceships, they look so cool! All the little secret smol characters you've hidden around are nice, and I've glad you've included a guide for finding them because I would probably not have been able to otherwise.
Kiara's warnings being in German are a nice nod to her and all, but I do wonder if it's more important that I know what the game is trying to tell me. (I guess the flashing red banner is already pretty clear that something bad is happening)
I can't honestly think of much other criticism than that. I think you did really well!