In the Love Live! series, UTX High School's A-RISE is the first school idol group featured. But, is A-RISE the first school idol group ever featured in the history of anime? If not, who is the first school idol group?
It's been 3 months since the question existed, well, if you still haven't found the answer yet, here it is.
Magical Angel Creamy Mami is the oldest Idol anime I could find. It has 52 TV epsidoes + 4 OVA aired back in 1983. It's a school idol group, but unfortunately I can't find the name of the group.
Creamy Mami is about a young girl, Yuu, who after seeing a spaceship is given the power to use magic for one year. She is also given 2 cats, Poji and Nega, to watch over and guide her. Using her magic powers to transform into the idol Creamy Mami, Yuu must work hard at acting, singing, helping her parents at their crepe shop, fighting aliens and bad guys, going to school, plus try to get the affections of her childhood friend Toshio.
Wandaba Style is the possible oldest Idol anime with a group name, yes, finally, but wait, it is not a school idol!
A J-pop group named Mix Juice consisting of four girls: Ayame, Yuri, Sakura & Himawari attempt to make it big by playing the first concert on the moon. Bankrolling this endeavor is the 13 year old billionare Susumu Tsukumo and his android, Kiku 8 who propose to go to space in an eco-friendly way.
Lemon Angel Project is about a group of high school girls forming a new Lemon Angel Idol Group, I think that is it, I'm surprised that the first school idol group was created only 10 years ago.
Lemon Angel was once the greatest girl band of Japan, but then it broke up and most of its members vanished. When a music producer decides to put together a new Lemon Angel, average high schooler Tomo Minaguchi is approached to audition for the group. Little does she know of the mystery behind the original Lemon Angel...
"School idols" aren't a real thing; the notion was invented for the Love Live! franchise.
Hence, it must be the case that the first school idol group in anime is whichever one is first featured in Love Live! - and as you point out, A-RISE is that group.
I know this is years late, but the first idol anime ever is Sasurai no Taiyou (1971).
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