So, the main character's male childhood friend was actually his sister who got lost in the convenient store 7 years ago because their maid was envious of their closeness. Then, by some unexplained circumstances, the little sister became a guy and was bros with the main character. Then the little sister/childhood friend's past was explained later in the series.
It's basically one of the characters I wrote for a play.
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Oh, I am one yet many.