Mikoto Nikki (みことにっき Mikoto Nikki) is a psychological thriller game created by Charon, their first game debut.
Matarou, a young boy at school, confesses his feelings for his senpai, Mikoto. She invites him over to her house for dinner. While she's making dinner, Matarou looks around the house and collects pieces of Mikoto's diary. As he continues his strange quest, he slowly realizes that Mikoto isn't what she appears to be.
Towards the end of the game, Matarou discovers three rotting corpses in Mikoto's closet. From what he had read from the diary entries, he deduced that two of them were Mikoto's parents and the other was Yukimaru, a boy who started dating Mikoto before Matarou. Mikoto then enters the closet and confesses that she locked her parents in her closet and "took care" of them. One day, they called her a demon child and Mikoto refused to feed them for a week. As a result, they starved to death. Sometime after their deaths, she met Yukimaru who seemed to give her life meaning again. Like Matarou, he eventually discovered the bodies and she kept him locked in the closet. She then asks Matarou if he'd run away like Yukimaru did.
Here, the player is presented with three options, which determine the ending (excluding the one involving the flashlight).
If Matarou heads into the closet without obtaining the flashlight from the box in the storage room, Mikoto will enter and hit him on the back of the head, probably locking him up inside the closet too.
Bad End 1: From Behind
If Matarou runs away from Mikoto, she will immediately catch up and apprehend him. The ending is left unclear, but it is suggested that Mikoto either killed him or brought him back to the house to be locked away in the closet.
Bad End 2: What You Wished For
If Matarou decides to stay with Mikoto, she happily says that she will prepare lots of food for him from now on. Then, she will promptly close the closet door and lock it, trapping Matarou inside, suggesting that he will share the same fate as Mikoto's parents and Yukimaru.
If Matarou hugs Mikoto, Mikoto will be moved by Matarou's actions and starts apologizing for what she has done. Months later, she and Matarou are still together, both shown playing in the snow. Matarou fondly notes how Mikoto's behavior has improved since he had accepted her.
- The game is loosely based on the anime Mirai Nikki and Mikoto's backstory is similar to Yuno Gasai, down to locking her parents in a cage and accidentally murder them. She's also mentally unstable.
- It has a sequel, Full Bokko Youchien, which is centered on Mikoto and Matarou's son.
- Mikoto's ex-boyfriend, Yukimaru, is the most recurrent character in the Charon universe. He later appears in MenheRafflesia as Itarou's best friend, in Fake Worlds End as one of the students in Taro’s school and in Dice Psycho and Vanilla: Garden of Judgement as Kazami's lover.