Yumeochi: Yume de Bokura wa Koi ni Ochiru

Even in university, Chono is stuck in the past regrets of his high school years. His dull days come to an abrupt end when he comes across a mysterious book... A book that allows him to return and re-do his high school life in his dreams. Follow Chono and the girls of his dreams as they reshape their wasted youths!
(Source: MANGA Plus)
Note: Includes four extra chapters.