Happy☆Lesson: Advance2003
Comedy
Harem
Slice of Life
Romance
This anime has a potential prequel!
Hitotose Chitose is now living together with his 5 teachers as his mothers when a mysterious girl appears and becomes their neighbor which turns out that that person is Nagatsuki Kuron who wants Mu-chan to be her mother so another sibling rivalry ensues as to who would end up as Mu-chan's child. (Source: ANN)