The Topic System is the main term of Tokyo Mirage Sessions ♯FE.
This System is used by Itsuki to receive messages from his office friends in real-time through the “Topic” tool, allowing him to communicate with his colleagues. The player can advance the story through these messages, and sometimes replying to these messages will result in side-stories that deepen their bonds with other characters.
The feature is about side stories, which are optional quests revolving around the members of the Fortuna Entertainment talent agency. These side stories occur when certain conditions are met, and by communicating with certain characters through the game's “TOPIC” social networking system.
Completing side stories will involve tasks such as having a date with Eleonora and taking her to see a movie or, as the trailer depicts, helping Toma with his dream to become a renowned actor. Completing them will also make characters more powerful in battles, giving them access to new skills.
When side stories for characters are completed, their Mirages will be able to change into a different class, similar to the Fire Emblem series. The example shown in the Nintendo Direct footage is Tsubasa's Mirage, Caeda, changing from a Pegasus Knight to a Wyvern Rider.
The game takes place in real world Tokyo locations, such as Shibuya and Harajuku. There are numerous stores that can be shopped at, such as convenience stores and accessory shops around the city. Money earned in dungeons can be used in these shops to purchase beneficial items.
In town, the player can visit the shops to pick up equipment. In the Heehaw Mart convenience store, the player can find useful items to fight against Mirages, and the shop posters and background music will also change. In the Jewelry Caravia accessory shop, they will find accessories that enhance various parameters. And at the Anzu Store Tokyo clothing shop, they find additional outfits.