Tatan (タタン, Tatan), renamed Tatiana in the Atlus localization, is the daughter of Blaire. While she has some training as a Craftknight, Tatiana is still young and has taken to the role of housekeeper (since nobody else in the family seems to care). She is innocent and looks up to her brother Orin and the player. She is a terrible cook but is always willing to show off her culinary skills, much to everyone else's dismay.
There's an Easter Egg hidden in the 5th day of the game, which the players would only find if they went out of their way to look for it.
In the Subterranean Bay there's an event in which an Aqua Elemental will block the way of the protagonists unless they ask him to let them through, but in a seductive manner. Since the protagonists are unable to convince him they ask Lynn for help, who is with Bruno in the Thunder Fortress, after some dialog Lynn will join the party and the player can go anywhere with her. If the player goes to his/her home Tatiana will be standing towards, if the player talks to her she will ask them what they are doing, The player is given the option to lie to her or tell her the truth, if they lie Tatiana will get furious at the protagonist and stay at home in the kitchen, if they tell her the truth, she will force the protagonist to let her go with her to the Aqua Elemental and try to seduce their way through. Once there she will attempt to seduce the Aqua Elemental and he will say that she was very close to convincing him and that she should try again when she grows up, then the event continues as normal. At the end of the day after the protagonist got the Daemon Edge, Tatiana will act awkwardly in front of everyone, if the player chose to lie to her she will still be mad at the protagonist. In both cases, if the player also has a night talk with Tatiana they will have an awkward conversation about being sexy.