* Eiji Tono, one of Kindaichi's classmates, [[spoiler: commits suicide due to Miyuki, whom he confuses for his late sister, despite murdering four innocent people and then trying to force his sister's actual killer to commit suicide as well.]] However, he was then seen again in ''The Undying Butterflies Case'', [[spoiler: suffering complete amnesia and with no idea as to who he once was.]] He falls in love with one of the Maradame sisters and they get married. Kindaichi and the others decide to leave him alone, figuring [[spoiler: the person he used to be is completely gone, and after the emotional torment he suffered before his amnesia, it's better to just let him have this new life.]]
* Playing the Fool Case:
** When Reika's been kidnapped, due to her trauma of seeing her real father being strangled, the kidnapper felt sorry for her thus becoming her father and treats her 'daughter' well despite being the kidnapper.
** In rage, Reika could not accept that his manager is his brother since he's a murderer too thus runs out of the heavy snowstorm. The manager manages to catch up on her and save Reika from an avalanche.
* Kindaichi the Killer!? Case:
** The start of the case happens to fall a few days before Miyuki's birthday. Her attempts to remind Hajime about it fail repeatedly after constant interruptions. Hajime's run from the law continues even onto the day itself, with Miyuki worrying so much about him that she forgets about it entirely. That same night though, she receives a message from Hajime, telling her to go to the park at 11 p.m., where she finds a box containing a small cake for her, with a happy birthday message, from Hajime who had already left the park, which she tearfully accepts.