More from the novel:
The funny thing is how the gay part at Christmas was also a lie told to the family. It was just an impuls Yohan had at the time and he was in no way attracted to any guys before Jun.
Also, the dad is a pos, he did abuse Yohan but always in secret until one day he hit him so hard Yohan forgot all his memories and his personality changed, his pathological lies also came after that. This all is only something we and Jun learn at the very end of the side stories.

Jun will hate yoohan ass more just wait