Mizuto and Yume used to date, but now they've suddenly become stepsiblings. Both of them agree that they don't want to do anything that'd disappoint their newly remarried parents. However, neither of them can accept the other as being the eldest sibling in the relationship. So they both agree to settle the matter with a game. Whoever does something in conflict with what people might consider normal sibling behavior, loses. Making them the younger sibling.
If I've upset you, I apologize.
.أعتذر إن كنتُ قد أزعجتك
Wenn du mir böse bist,
entschuldige ich mich.
Perdona si te molesté.
Perdona si he metido la pata.
Si tu veux, je me tiendrai
hors de ton champ de vision.
Se ho fatto qualcosa che ti ha turbato,
ti chiedo scusa.
Peço desculpas se te irrito.
Прости, если обидел.