Stargazing: Seio Gakuen Koka (Gakuensai Version) - Horie Yui
I consider ufotable to be a rather solid animation studio. While they are more well-known for their excellent quality series and movies like Fate/Zero and the Kara no Kyokai films, Gakuen Utopia Manabi Straight! is a series that not many seem to have heard of.
It's fair, given the strangely unique character designs and the even stranger setting, taking place in a future where birth rates have vastly decreased. Regardless of what it presented, seiyu veteran Horie Yui fronted the show, giving it and this insert song that classic charm.