Sister's Log

is a Japanese comedy manga by Kenji Tagushi that serialized on Shogakukan's Weekly Shōnen Sunday magazine from 2012 to 2016, completing up to 300 chapters and 12 tankōbon volumes.

A special 3-episode OVA was released as limited edition bundles from volumes 5 to 7.

Plot
When Konoe Moyako and her little brother, Akira, were young, he said he wanted to marry her. Naturally, Moyako decided that her little brother was a complete pervert who was obsessed with her. Now that they're both teenagers, Moyako is convinced she needs to "rehabilitate" him. However, it seems that the "perversion" is entirely in her imagination, and she can't seem to help turning completely innocent situations into creepy ones in her mind!