Chiaki-kun Mimamori Club

On his way to school, high school boy Taisuke Koma is approached by a stranger who says to him, "We finally meet again." Koma is surprised, but later that day during class he is introduced to a new transfer student, Kei Chiaki—the same stranger who approached him on the street. What's more, Chiaki claims to be Koma's childhood friend...!?

(Source: Kadokawa, translated)