A Japanese black haired girl named Zero lives with her grandparents after her mother mysteriously passed away. Her grandparents, papa Namiki and granny Chikara decide to lie to Zero for her bittersweet innocence, and not let her know. By the time Zero is old enough, she is gifted with her mom's once huge diary, all of the pages her mother wrote on carefully and effectively pulled out, with a "Laugh!!" sticky note put on the front by Chikara and the quote of "The only person you should try to be better than is the person you were yesterday." above it and to the side, to cheer up the covers atmosphere. "横たわって、死んだ子供時代よ!ゼロ、私の名前よ、ママ?なぜ私のソケットのように空虚なの?"