Ano Hi Mita Hana no Namae wo Bokutachi wa Mada Shiranai.

In Chichibu, Saitama, a group of six sixth-grade-age childhood friends drift apart after one of them, Meiko "Menma" Honma, dies in an accident. Five years after the incident, the leader of the group, Jinta Yadomi, has withdrawn from society, does not attend high school, and lives as a recluse. One summer day, the ghost of an older-looking Menma appears beside him and asks to have a wish granted, reasoning that she cannot pass on into the afterlife until it is fulfilled. At first, he only tries to help her minimally because he thinks he is hallucinating. But since Menma does not remember what her wish is, Jinta gathers his estranged friends together once again, believing that they are the key to solving this problem. All of the group joins him, though most of them do so reluctantly. However, things grow increasingly complicated when his friends accuse him of not being able to get over Menma's death, as they cannot see nor hear her and believe Jinta is hallucinating. Menma shows her presence to the group in order to prove that she is indeed real. All the group members eventually wish to shoulder the blame for Menma's death and long-hidden feelings among the group are rekindled. The group struggles as they grow from trying to help Menma move on and help each other move on as well. (Source: Wikipedia)