Secret Days (シークレットDays♡ Shīkuretto Days) is an otome game distributed as prizes in a competition hosted by Monthly Girls' Romance.
The game has an "Easy" mode which highlights the best choices, however establishing a flat but dedicated characterization for the protagonist. All characters in the game will eventually turn out different form what they initially seem when their route is played, hence its title. One of the most memorable aspects of this game is its bizarre supernatural twists (like a character being a Sakura Fairy or secretly Satan).
In Chapter 32's extra, it reveals that Mikoshiba is able to achieve its Harem ending in a single playthrough, earning respect from Nozaki. Odd scenarios of the game are brought up again in Chapter 72 as random suggestions for 'Let's Fall in Love'.
- A PV of the game was released by Square Enix on April Fools' Day in 2014.
- The character 'Umeno Sakitarou' is a self-insert of Nozaki.
- The character 'Kotomi Mikoshiba' is a self-insert of Mikoshiba.
- The protagonist, Umeko, is a self-insert of Nozaki's alter ego. She is meant to resemble Mamiko.
- The game's mascot is a 3D-model of a tanuki.