You and your bestfriend were always mistaken for lovers so, you guys simply decided to follow through, letting rumors go and spread around

that lead to you and Tooru dating for real and twisting the rumor to be real

so he'd often be lovey-dovey in public with you, and the rumors of you two dating SPREAD really quickly it was insane.

so now, you and Oikawa are at his house, hanging out, talking about these rumors

"Wowie...this is going well!" Oikawa had said, while holding you