Mikami-sensei's Way of Love(2014)

Mikami-sensei no Aishikata

Without a single boyfriend in sixteen years, Natsume has zero relationship experience … and it’s all thanks to her super overprotective neighbor—high school teacher, Mikami-sensei!! Whether at home or at school, Natsume is always being manipulated by his strangely overbearing affections. But while it may have seemed like sibling love at first, their relationship soon takes an unexpected turn … !

(Source: Kodansha USA)

Note: Contains six extra chapters.