Yomi was named by her grandmother, before the latter's death, after her dead dog, who was also named Yomi.
Yomi, before she died, was kept in the hospital due to a deadly illness. Because of this, she could never go out and play, which was something she always wanted to do. Upon her death, she became a ghost and was greeted by her grandmother, meaning that she previously died as well.
Yomi has a unique personality; she is, for the most part, happy, but can also have mood swings as well. This is observed when the player tries to talk to her at times; she can be happy once, but then be sad or angry the next time, possibly due to the player's actions.
Like any other character, her feelings can be hurt. Although she doesn't really take effect, she does get angry at the player, should they do any action that will anger her or hurt her feelings.
Yomi, as a Super Player, is a pitcher. As with all other Super Players that pitch, she has a deadly Super Pitch that will most likely lead to a strikeout.