The anime is Grisaia series, specifically the main series, composed of two seasons and a special. Grisaia no Kajitsu, Grisaia no Meikyuu: Caprice no Mayu 0 and Grisaia no Rakuen. The work is based on a visual novel of the same name, and it is available on steam. I recommend watching the anime. There is, a "sequel", albeit with new characters and changing the focus of the story. I don't particularly recommend it, but anyway.