It sounds terrible, 'Lolita'-like, but in 'Choki', it might be very different:

Naoto & Kyoko are a happy couple. Saki, a 7-year-old girl attends Kyoko’s calligraphy class. Abused by her own mother, between Saki & Kyoko, some kind of daughter-motherly relationship grow.

10 years passed. Kyoko's died and now, Naoto lives with the memories of his beloved wife. Saki, now blind, suddenly shows up, looking for Kyoko. Kyoko isn't there anymore, but her memories bring Naoto & Saki together. Gradually, they grow feelings for each other, but this is like a taboo for Naoto: How can he be in love with his beloved's 'daughter'? How can he betray Kyoko in this horrible way?

It's up to the audience to decide if the relationship is fine. To me, though very complicated, the relationship is like a present from Heaven by Kyoko for these two aching souls: I wish them the best!