Actually, Star Beats! is also a song that I often play when I want to sleep. But since I mentioned it in the previous comment, I'll choose this song.
16:20 ~ (covered by) Kikuchi Akane
Not the opening or closing song of the anime Joshikousei no Mudazukai, but just an insert song in episode 11. Original Song from a YouTube account TeishotokuP...
Hidden Spoiler Text
...who is the husband of this Anime mangaka. And this anime is "rumored" to be the true story of the two of them.