Kanojo ga Boku wo Taoshitekurenai  

Yuusha ga Maou wo Taoshite Kurenai, 勇者〈かのじょ〉が魔王〈ぼく〉を倒してくれない

A high school student named Munakata Shizuya was suddenly transported to an alternate realm without any explanation. To return home, he must guide a newbie warrior and have her vanquish him in battle, yet there's a catch - she can only do so if she successfully defeats him first.