6-gatsu no Love Letter
From Chibi Manga:
Momoko is an absentminded first year senior high student who makes a lot of careless mistakes. She is able to keep pushing on thanks to her best friend Mahiru's support. Lately, she has been interested in a classmate, Igarashi-kun, who is very my-paced and always late to school! (A feeling of fellowship!?)
One day, Kujou-kun, the person who is always with Igarashi-kun called out to her. He asked her to wake Igarashi-kun who lives alone, up each morning and take him to school for a whole week...!?