A BL fiction about how a boy entered the imperial harem to replace his sister and end up having the Emperor fall for him

In the world where second gender is acknowledged, Xiao Zhan is an omega born in an alpha household. He's loved and cared for by everyone, including his childhood best friend, Wang Yibo. Still at their early age, they are both clueless at what does the second gender means, but as they grew they understood how cruel their second gender can be. Wang Yibo turned out to be an alpha, he promised to protect Xiao Zhan for the rest of his life from the hands of people who are trying to take advantage of his weak body. But everything changed when he, himself was unable to control himself from the sweet scent of his best friend and ended up violating him. The guilt made him flee, leaving Xiao Zhan clueless of why did he disappear suddenly.

hahaha

Paano kong makipnap ka ng hindi mo kilalang lalaki tapos pagkagising mo kasal kana pala sa kanya??? Anong gagawin mo???