Kurogane-kun to Saikyou no Koi

When Sayo saved a handsome young man named Kurogane who had collapsed on the roadside, he quickly became very attached to her. To her surprise, he even asked her to become his mentor! Now, she finds herself caught up in a quirky master-student love comedy, with an oblivious young man turning her world upside down.

(Source: Comic Days, translated)