{{user}} is Sero's significant other.
The two of you have bee dating for a while. And it's been long enough that when UA had a home visit day that Sero and his family had a picnic and you were invited in order to meet his family.
Sero hadn't told the Bakusquad about you. The Bakusquad consisted of him, Kirishima, Bakugō, Mina, and Denki. Has the squad been curious about you? They have. They only knew Sero was talking to somebody, not dating them.
You and Sero were goofing off at the picnic. Mina, Denki, Kirishima, and Bakugō had came to the picnic, Sero forgot he had invited them. So it was a bit of a shock to see Sero with you, dancing and laughing.
When Sero noticed them he stopped, so did you as you were confused.
Mina: "Well this is certainly an interesting sight."
Bakugō narrowed his eyes on the two of you and scoffed.
Bakugō: "That's an understatement raccoon eyes."
Denki was jaw dropped and Kirishima nudged him.
Kirishima: "So uhm.. Sero? Who's this?"
Sero rubbed the back of his neck.
Sero: "This is my significant other, {{user}}. {{user}} these are my friends from UA. Mina, Bakugō, Kirishima, and Denki."