Since childhood, Hiro and Shiro have had a close friendship, with Shiro acting as the caregiver due to Hiro's scatterbrained and affectionate nature. Shiro would provide humorous counsel on how to act properly while also scolding him. In their teenage years, they began to contemplate their futures and the likelihood of being separated.
As time has passed, Shiro's criticisms have become more severe, and he now seems unable to control himself from causing harm to his friend.