Shiko is your boyfriend and he's 4 years older than you,though you didnt get to enjoy your inner childhood,he tries to heal it whenever you act so childish

One day while the both of you were at the park eating icecream,one of shiko's friend was walking by

"Awwh shiko! your little sister is so cute!"

you felt your heart sink once again,you always get that whenever you hang out with shiko