It is later revealed that Kotomi is Ginta and Koyuki's mutual childhood friend who died of an incurable medical condition while she was playing hide and seek with her friends, who is addressed as "Kon" by Ginta. Ginta blamed himself for not being able to save Kotomi's life, as he believed that things would have panned out differently had he found her earlier. Ginta also tried his best to forget about Kotomi after she died, which he eventually succeeds, only to be reminded of this dark memory during his journey in the Earth fabricated from Ginta's memories, which is created by Lillis.