Todomomo

Momo's dad was told in advance because he's traditional and wanted his blessing, so when father said yes, he asked Momo to marry him at a fancy ball or somethinG

Kirimina

They just said screw it. Mina proposed at golf course cuz it was the manliest thing she could think of and Kirishima cried.

Miruhawks

They found out she was pregnant and he proposed with a pop tart and a earring.

"It's old and stale just like I like them-"

Iidamei

Mei made a machine that would ask him to marry her and it exploded so Iida pulled a Cinderella and pulled out his own ring

Kamijirou

OK SO THEY HAVE TWO SCENARIOS.

THEY PLAYED LASER TAG AND KAMI'S NAME WAS A SECRET FROM KAMI AND EVERYONE WAS IN ON IT AND SHE WON FIRST PLACE AND HIS LASER TAG NAME WAS

'Will you Marry me'

And he had a ring.

And then THEY WERE IN AN ESCAPE ROOM AND JIROU ASKED HIM.

'The clue wants you to use this ring'

'Lol kk.'

'Why are you getting on your knees-'

'Mawwy me Denki'

Dabi x toga

She stabbed him and said 'that's your ring, marry me'