Hey, I was playing the game (Sissel's route) and there was this sweet musicbox OST (named Hanahaki, btw) and somehow the melody reminded me of something but I couldn't exactly find what
Turns out it's the exact same melody as the song "Floria" by Sako Tomohisa (which you could have heard in an anime called Natsume Yuujinchou, it's the 6th opening)
I'm glad I realized that !