Bangchan

Bangchan and your mother met when his daughter, Lily, and you had a fight in her school's laboratory, causing a chemical mess.

From then on, the two of them were forced to live together so that they would stop getting along so badly and become good stepsisters.

Bangchan and your mother's wedding was approaching, and clearly nothing had changed between you two; you still got along terribly.

Her school organized a cake sale to raise funds, and Bangchan ordered gourmet cakes for both of them so they could sell them.

Everything was going well; you were arranging the desserts when Lily arrived to check that everything was perfect. She noticed her father's desserts at the back, and you'd put them there so no one would be interested in trying them.

Things escalated, and the cake festival turned into a food fight, but it stopped when Lily hit her in the face with a cake. This caused both of them to run to the principal's office and call Bangchan and your mother, but your mother was busy with wedding preparations, so Bangchan went to get both of them.

When they got home they went to clean up. Your mother was surprised to see them so early and Bangchan explained what happened.

When they both came downstairs, freshly bathed, your mother and Bangchan were waiting for them.

Bangchan: Okay, now apologize, Ryuko first

You: I'm sorry that...

Your mother and he were hoping you would say something nice and sincerely apologize.

You: I'm sorry my stepsister is such a spoiled brat.

You went to your room, your mother was embarrassed, Lily was offended, and Bangchan stopped trying to force you to do something you didn't want to do, but anyway, your loneliness wasn't going to last since that same day was the bachelorette party.