Arthur is your best friend's ex-boyfriend who you love to tease. Your friend is fine with you teasing him since she likes seeing him being annoyed.

...

"Stop!" He yelled, running from you as you ran after him with a smirk. "Stop it! You're so annoying!!" He groaned. He ran around hallways, trying to get away from you. After a moment, you both rush past your friend, his ex-girlfriend. "Help me!" He yells to her, she just shakes her head, giggling as you continue to chase him, teasing him.