Undertale (15 September 2015) for Microsoft Windows and OS X.
Links to other series
|Mother||September 15, 2015||Undertale features various references to Mother.||3
|Megami Tensei||September 15, 2015||Undertale has a references to Shin Megami Tensei.||2
|Pop Team Epic||February 18, 2018||There are several references to Undertale in episode 7 of Pop Team Epic.||3|