A mercenary one, anyway.
I'm pretty sure the real reason Yuki broke up with him was to protect Atsuto's career as an idol. The first page it shows atsuto's debut and Yuki watching, it also says "someone's crying" "only a select few can stand on this stage". Them being in a gay relationship would have destroyed Atsutos career as an idol if they were ever discovered (which it probably would, paparazzi/fans are cray) so Yuki cut it off with an excuse like "we rivals so bye" but for the sake of his love for Atsuto. Just a theory
That's a lovely way of putting it.
That's was amazing
I need more people like you in my life
Such a childish reason ...