They're members of the popular girl band berryz koubou. the band that made the inazuma eleven anime ending songs: seishun bus guide, ryuusei boy, otakebi boy WAO!,maji bomber, shining power (the ending isn't on youtube so link to full song instead)

looking at the inazuma eleven wiki, they were also characters in an earlier game- inazuma eleven 3: sekai e chosen- as part of the pristonberryz team, which can be challenged after finding a concert ticket in a chest.

so I searched for other members of berryz koubou in the game and no one else showed up,

then I used the team from the old game as a guide to find other characters

and found ton nino (the lead singer of the group T-Pistonz+KMC) in whistlaria constellation....both of him.

same name and description

see, the editors over at inazuma eleven wiki found him before me and that's how I now know why there's two of him. for the pre inazuma eleven 3 games he had a completely different design that was then changed to actually look like him.

In Chikita is another member of the group I found and he's in the tornadrix constellation

(excuse the tangent but besides the fact that i cant find the member shu maimai, i noticed that there are characters shuu and mai that are siblings appearing in the inazuma eleven go movie: ultimate bonds gyphoon)

anyways the group made all the inazuma eleven ops

I couldn't find others but a) the game's player search isn't easy maybe i missed them and b) there is still going to be an update adding characters from inazuma eleven go galaxy and inazuma eleven orion, so they might show up then

edit: found Kota! (odenius)

so the the T-pistonz+KMC group had disbanded back in 2014. ton nino together with Kota formed pugcat's: the band that made the op songs for the orion season. and is part of the new T-pistonz

besides them ill also point out the sorano aoi (odenius)(supportus) morimura konoha (braceletara), mizukawa minori (ferrum turis) and senno marika, all are characters whose voice actors made inazuma eleven ending songs.

sorano aoi's voice actor, kitahara sayaka, sings the ending theme all songs for the ina11go anime and for the galaxy season. she and the voice actresses for morimura konoha and mikuzawa minori, yuki aoi and takagi ayahi respectively, form the group COLORS.

“I will study women's feelings by reading my favorite girls' manga."