Kataomoi Shrink

Toranosuke is in love with his childhood friend, Sumire, who's two years older than him. However, Sumire fell in love with the older brother at the coffee shop... But her first love is shattered, and as she find herself in a surprising situation, will the hero, Toranosuke, be able to protect her from danger? A mysterious love comedy between an older clumsy heroine and a younger crafty guy.

(Source: Comico, translated)