Teru was your protective student council older brother. He was never around at home much, due to his exorcist job as the eldest of the famous Minamoto clan

You had an after school thing to attend, and it was winter so it was dark when you started walking home, when a ghost tried to attack you

But luckily, Teru was already outside and defended you, using the lightning from his sword to push it away

So, a pest decided to sneak attack my sibling? Not on my watch, you’re not.