Seiko ???

Seiko ??? (セイコー不明チャプター), is a spin-off game based around the Seiko series.

Information and game play footage was first released at the Sony Computer Entertainment Japan Asia Conference on September 9, 2013. The game was published on September 25, 2014, in Japan for the PlayStation Vita and is also compatible with PlayStation TVs.

At the NIS America’s February 19 press event, it was confirmed that the game would be published in the West. The localized game was released in North America on September 1, 2015, in Europe on September 4, 2015, and in Australia on September 10, 2015. The Western release includes both Japanese and English audio.

Seiko ??? takes place between Seiko and Seiko 2: Abandon Hope.

A PC release of the game was announced on November 18, 2016. On the same day, NIS America confirmed a PS4 port will be released on June 27, 2017, and later on June 29, 2017, in Japan.

Synopsis
"Shiro Kamichiro is a commoner, the kind you can find anywhere. She evacuated to the Project Riku to seek help along with her sister, Seiko Kamichiro. After Kiriko Saikyo getting affected by the virus, Shiro started to lose hope but she still tries to find a shelter. She imprisoned herself in an apartment to save herself but she also needed to escape in her own prison, wishing that this chaos will end soon. But one morning, she was forced to learn even deeper despair when someone suddenly broke down her front door. But it wasn't a hero or a savior...

It was a virus

After escaping from the merciless virus, Shiro can't believe what happened outside while imprisoning herself for half a year. A world full of viruses infecting people falling into despair caused by someone named Kiyo Matsuzaka. A noble lady named Chisa Kirisaki has came to save her from the viruses, and that giving Shiro more hope." - Official Synopsis

Gameplay
Seiko ??? is a RPG Maker adventure shooter game where the player controls Shiro Kamichiro as she tries to survive in a city overrun by viruses with the help of her partner, Chisa Kirisaki.

During the game, the player has the option to switch between playing as Shiro and Chisa. Choosing to play as Shiro allows the player to utilize a cube-shaped glass hacking bomb which turns her words into various types of ammunition, called Truth Explosions. Initially, the hacking bomb has an unlimited stock of every type of Truth Explosion.