This was so funny and cute I loved it so much! The characters compliment each other so well, I just adored their interactions and dynamic. Both designs were great. I especially loved the various expressions, they were so lively, comical, and paired perfectly with the writing, conveying a good sense of the character's inner thoughts and emotions. The inner-dialogue captured the experience of the confusing conflicts of both friends-to-lovers and exploring one's sexuality quite well! It was playful and humorous, but also very respectful and relatable.
My only complaint in the way of constructive criticism, was I got a little confused when the conversation with the sister happened off screen. There was some mentioning of things which I assumed were references of the main story this is based off, though I haven't played through that game yet, so I felt I little lost. Also the sister called her brother "Pumpkin", which in retrospect, I just assume is a nickname. Though at the time, I was confused as to whether it was his mom or sister talking to him, as it seemed more like the sort of nickname a parent would give their kid as opposed to sister and brother.
So my suggestion would be to include the name with the character dialogue, especially when the character is off screen. I saw the sister is getting a character sprite in the future, so that'll definitely help, too I think.
I enjoyed this one a lot and am looking forward to playing the full version when it's released! I am curious in checking out the other vn this one was a spin off for as well. :3