Games like Ef: The First Tale.

If you finished Ef: The First Tale., the closest matches are Milk Outside a Bag of Milk Outside a Bag of Milk, Opus: The Day We Found Earth, Dies Irae: Amantes Amentes, Tsuki ni Yorisou Otome no Sahou and Mystery of Rivenhallows. All 7 share its adventure genre and are ranked by how closely their themes and modes overlap.