this is not what jocey thought they were getting when they asked this

Arashi Narukami: Yumenosaki Academy Idol Course Second Year, 16, model, captain of the track and field club and temporary leader of powerhouse unit Knights in the wake of their actual leader taking a break from school and the only other third year doing things like kidnapping other groups' members bc he's a fucking creeper. Arashi consistently refers to herself as 'big sister'.

Mika Kagehira: Yumenosaki Academy Idol Course Second Year, 16, member of the two-person unit Valkyrie, formerly a group so famous they appeared on TV that is now on almost complete hiatus. Mika lives with her group leader because her family is in Kansai, she pays rent but sends the rest of her money home. Mika has heterochromia and is anxious when dealing with strangers and men. Mika's accent reads like Kyoto-ben so I'm gonna guess she's from around there but don't quote me until we have confirmation lmfao.

Mika and Arashi have been in the same class since they were first years. It's worth noting that Arashi introduces herself to the player by telling her she can call her "Naruko", and the people who show any respect for her call her some variant of "Naru" unless they're using "Narukami"; one character calls her Arashi-chan-senpai but that's just bc Mitsuru is the most casual character I've ever seen, lmao. She calls Mika Mika-chan and Mika calls her Naru-chan, I'll note that Mika says she thinks her first name is "girly" even though her last name is totally suitable and the only other person who calls her Mika is Nazuna.

ARASHI LINKS:

Sub story 1 (alt link), Swaying in the Wind Substory (alt link)

MIKA LINKS:

Sub story 1 (alt link), Scarecrow's Wish Substory (alt link), Song of the Garbage Dump Substory (alt link).

The substories are character intros to the player character; I threw Arashi's on pastebin bc I can't remember who posted it off the wiki and I'm too lazy to track it down, I won't tell if you won't. Swaying in the wind's first half is important for Arashi but the second half is less so ig. Mika doesn't have a ton of content so I'd suggest reading all of her translated substories! I just unlocked Arashi's second substory so I'll give it a summary when I've had a little time.

ARAMIKA LINKS:

Mika was introduced late into the storyline: Enstars is currently repeating the school year over so they can fill in the time gaps/milk the third years for more cards, so Mika has appeared in minor roles but the majority of her character was revealed in the flashback event Reminiscence.

The Wiki has a full index of all the stories, Arashi appears in Girls Talk 1 and 2, Marionette is a long event so I don't blame you if you want to skip around but Mika is really cute in all of it, so.

Here is a mirror of that translation at the tl's original blog on LJ in index style. It's all marked so same notes as above!

Characters in Enstars appear as "Event" characters in particular venues. Both Mika and Arashi were "Event" characters during Marionette, and all of Arashi's Events are from Mika's POV. Mika also appears as an "Event" character in the 2-B course, and she has a Special Event that mentions Arashi, but there don't appear to be translations atm? I'll do them really quick when I'm not grinding EXP lmao. She does literally say "I - get real uncomfortable around boys, since I grew up surrounded by girls. And talkin' t'Naru's just like that, y'know? I really like Naru." let me live, mika.

Arashi's Normal Events + Arashi's Special Events.

If you want a rundown of All Arashi Content, the wiki is honestly the most convenient bc it keeps it all together. She appears in the main story but no one wants to translate that bc it's super boring. All you need to know is that Knights lost and their previous temp leader, Sena Izumi, was banned from performing by the school for kidnapping a member of the MC unit Trickstar. Arashi's appearances in the gacha stories/event stories are (in enstars timeline order rather than real life order):

Sweets (Knights Gacha)
Ballet (Knights-Ra*bits Event)
Duel (Knights-Trickstar Event)
Holiday (Multi-group Gacha)
Rebellion (partially fully translated) + Full summary) (Knights Event)
Greek Legends (Track & Field Club Gacha)
Phantom Thieves (Knights-Ra*bits Event, Ra*bits-centric so skip around if you're just here for Arashi)
Chocolat Fest (Trickstar-Ra*bits, but the senior members of the Track & Field Club appear)
Beauties of Nature (Knights Gacha)