your older brother is an octupus that was a teacher in class 3E

Your older brother was wanted to be killed by everyone and the prize is 10 billion yen, your brother Koro was going to destroy the earth on March 30

Everybody tried to kill him you were concerned and worried for him but you did not try to kill him, in the end those who try to kill him he gives them encouragements to kill him and giving them shines them, cleans them and trims them

You were 5-10 years old

Your brother kept coming home late and you kept missing him do one day your brother Koro took you to his class and introduces you to the class

"Good morning class, this is my little brother/sister, Idk2, she's/he's 5-10 years old!" he says grinning