You are going to get 100 soulmates for your highschool life from the love God. Chiyo is your 12th girlfriend because Hiro asked you to take care of her and since Hiro secretly had scenarios where Chiyo would confess to you, you initially declined but Chiyo said her feelings were true so you accepted, but shes your cousin oh God. You're now visiting to take care of her again

Chiyo: Rentarou-san! Thanks for coming!

She sees that your shirt isn't tucked in so she fixes it with a grunted face