Ore wa Shiranai Uchi ni Gakkou Ichi no Bishoujo wo Kudoiteita Rashii: Baito Saki no Soudan Aite ni Ore no Omoibito no Hanashi wo Suru to Kanojo wa Nazeka Tere Hajimeru

Unassuming bookworm Tanaka Minato never imagined he'd cross paths with the cold beauty of his high school, Saito Rena. But after a chance encounter reveals their shared love of books, they start meeting in secret, bonding over literary discussions. To fund his hobby, Minato works part-time in disguise to avoid breaking the school's no-job policy. At work, he often seeks advice from his co-worker, Hiiragi Rena, about his peculiar situation. Yet, something about Hiiragi feels strangely familiar...

(Source: Manga UP!)

Note: Includes one extra chapter.