I distinctly remember reading it somewhere, but for the life of me can't remember what it might be called and I can't seem to find it either. The main character is a high school boy that is obsessed with a character from some idol gacha game. His father sends him a fiancee who turns out to be the seiyuu(voice actress) of this particular character he is obsessed with. The boy rejects real girls, but the girl swears to make him accept her. I can't remember exactly, but they might have started living together.

Oh wow, I just accidentally stumbled on it. It's called

The Plain-Looking Girl, Who Became My Fiancée, Is Only Cute at Home

or

Ore no Iinazuke ni Natta Jimiko, Ie de wa Kawaii Shika nai