Meiko died in an accident as a child, but appears before Jinta on a summer day. Although she is aware of her death, Meiko is talkative and lively. She greatly values the childhood memories and friendships she once shared with the others, but has very few memories other than recollections of her friends and family, including that she had once made a request to Jinta.
When she appears to Jinta, she has aged somewhat, but still retains childlike speech patterns and tendencies. She is also clothed in the dress she was wearing the day that she died. Though only Jinta has the ability to see or hear her, Meiko appears to be able to interact with the world around her: opening doors, cooking food, eating, and even playing video games, with many of these activities shown in scenes without Jinta present.
Characters that she embraces often feel that the air is heavier. She held Jinta in special regard when she was alive and still worries about his current state. The others call her by her childhood nickname 'Menma', and she similarly refers to the Super Peace Busters by their childhood nicknames. Jinta has stated that she is selfless, only crying when others are hurt.
Meiko holds no grudges towards her friends for the accident and hopes to pass on so that she can be reincarnated and once again live in the same world as her friends.
She has feelings for Jinta and even when she returned as a ghost, still held those feelings. In the last episode, she states that her kind of "love" was the love where she wanted to marry him.
It is later revealed that Menma came back in order to fulfill the wish of Jinta's mother to teach Jinta how to cry and let out his feelings
On some particular day in their hideout, Naruko asked Jinta if he liked Menma. With this question he felt embarrassed and acted impulsively, calling Menma "ugly" and ran out. Instead of crying, Menma smiled and chased the embarrassed Jinta. It was never actually shown what happened to Menma, but the anime indicates that she slipped and fell while chasing Jinta and drowned in a river nearby.