"Until you find someone you like more than me, once a year, on your birthday, I will go on a date with you" are the words Hayate said to Takashi who confessed to him on the day of their high school graduation.

It has been ten years since then, and Hayate has diligently followed through with his promise to Takashi, but instead of his feelings fading away — they've only increased.

Thinking that he cannot continue with unrequited love toward his straight friend, Takashi lies to Hayate saying "I've found someone I love..."

(Source: Kadokawa, translated)