Boku To Majo Ni Tsuite No Bibouroku summary:

Wataru was picked up by a 100+ year old witch in a certain forest when he was a little boy. Some time later, he began to write about his daily life so that he would never forget those lovely days he spent with her and her cat Hotaru. When he began to have "special feelings" for the witch who raised him as a member of the family, he realised that one day he would surpass her age... A sad love story between a witch and a human that slowly passes through time.