Shit tier headcanon DO NOT READ
So I always likened Marisa's early childhood to that of Matilda in that movie. This is based on the fact that both main characters have magic powers and bad relationships with their family. Anyway Rinnosuke basically takes ip the role of Ms Honey and adopts Marisa and all is well. Meanwhile at Marisa's fathers shop, business has fallen rapidly since Marisa's leaving and the store accumulates rubbish and junk. After time, the store becomes infested by evil spirits, but Mr Kirisame refuses to leave his business. Eventually he is transformed by all the negative energy and garbage into a youkai. The news reaches Marisa and she heads off to fulfil her duty and bring balance back to Gensokyo. Marisa must finally confront her father; Danny DeVito - The Trash Man.