Monster Girls - My Oni GF

Oh no, now this guy has to deal with her scary-looking larger older brother in the later chapters, only for it to be revealed that he's actually a really chill dude is is thankful that the main character has the mental strength to deal with his bratty socially-awkward little sister.
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But none of that will matter when even LATER ON he meets her mountain-sized disapproving dad who would rather see her hook up with another oni, preferably the son of one of his oni business associates.
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Unbeknownst to him, the MC already met him cause they're in the same class and already had this rivalry 2 volumes ago, which ended in the son's admittance that he's only trying to hook up with the oni girl to make his parents happy, and is ACTUALLY attracted to the nerdy half-goblin girl cause they're both in the programming club.

Said half-goblin girl is considered "best girl" by a surprisingly large portion of the fanbase due to her ugly-cute appearance.