Sensei, Tokidoki Seifuku de Kiss

Ai Mamina who failed to make friends in school, started skipping classes. The form teacher in class, Mr. Kawagoe then conducted a house visit to Mamina's house. In order to let Mamina return to school, he proposed an idea to spend that following weekend secretly with Mamina alone, as students in school. That alone time between them gradually turned into something more... The secret high school Life which no one can know starts now!

(Source: ChibiManga)