Tonari no Yasaka

Since they were kids, Kaoru and his childhood friend Houko have had one rule: the loser in judo buys the winner a meal. But now that they're in high school, Kaoru just can't keep up—Houko only gets stronger every year, and he's stuck paying the bill. Then, after one crushing loss too many, Houko teases him with a single remark... and Kaoru snaps. He stakes everything on a final match: "If I lose this time, I'll buy you meals for the rest of my life!"

(Source: Kodansha, translated)