Because the author said it’s not. That’s why a lot of people are confused. Despite the juicy mini comics of them kissing each other’s cheek, highly suggestive actions - it’s only a bromance. The author even said that a kiss might not even be possible.
NOT YALL TRYING TO FIGURE THE GUYS GENDER AND IF THIS IS A LOVE STORY. YES YES IT IS ITS A SLOWBURN AND YES THE GUY IS A MAN AND YES HE JUST TURNED 18