9-nine- is a five-episode series. Episode 1 first launched for PC in April 2017 in Japan, followed by Episode 2 in April 2018, Episode 3 in April 2019, Episode 4 in April 2020, and New Episode in April 2021 as part of the full 9-nine collection. Episode 1 through 4 are currently available for PC via Steam in English.
The console versions of 9-nine- will include all five episodes, though Palette notes that there may be some changes.
Here is the game’s story synopsis, via VNDB:
A city that other than being a academic town, doesn’t have any special characteristic.
There have been some attempts at revitalization in order to attract tourists, but it achieved no success. However, for an unexpected reason the city began to gather the people’s attention.
Niimi Kakeru is a boy that despite the hasty attitude, has a strong sense of responsibility. He seems to be an ordinary student with a kind personality, but after a sacred treasure of a certain temple got damaged, an unusual power woke up on some youths including him.
He was supposed to be an ordinary student living in an ordinary town, but… now the young ones are involved in this mysterious fate.