This is the second TV ending. The song does not start when the credits begin rolling, but a moment before, where the images below were captured. I can't confirm it, yet, but the song, Ruretto Kyandoru, sung by Pure (Sayama Riko and Adachi Mari), seems to be in Kakyuusei Anime Soundtrack (KLCA2018).

Spoiler Warning!!!!!

Before you click the link below, which contain some captured pictures of the second TV ending, a few words are neccesary. With this episode, the TV serie ends; the bangaihen is a side story, without any relationship with the TV serie, except for the characters. So, why the spoiler warning? Well, since it is THE ending of the serie, it sort-of tells what each character does after graduation (and that includes Miyuki and Ai). Think it as an added surprise... ^_^

Kakyuusei TV Second Ending

Note: All images and characters are copyright of Elf, KSS Studios, and Pink Pineapple. They are being used without permission.