Story: 8/10
At first, I expected so much. Then I got disappointed, because I didn't think it would go the way it chose to go... and then I absolutely fell in love.

Let me explain: Maina appears in front of a put-together Eripiyo one day, asking her to come and see their concert. Eripiyo does not know anything about idols - but goes and immediately falls in love with Maina. Her obsession grows, and Eripiyo changes completely.
Owning only one pink-salmon jumpsuit, she supports Maina with everything she has - shaking her hand, buying her merch, spending every last cent on her.

But while Eripiyo speaks 10000 words during the 5 second hand-shake, shy Maina cannot get her feelings across. It's extremely problematic so with the help of everyone, she slowly builds courage, while reaching for Budokan, front row on the stage and much more...

It's so simple, yet it works so well. It's almost an allegory on idol culture in Japan (as a lot of people said too), bringing a bit of comedic (almost ridiculous) moments and a bit of backstage information (with few scenes about the idols themselves). For example, Eripiyo getting hurt and sick all the time from overworking herself, or her & Kumasa waiting for a 16:00 o'clock even at 4 am. Pushing herself until she breaks her throat multiple times... And then rumours - like with Sorane and her alleged boyfriend; which costs her her fanbase.
But at the same time, we see devotion - supporting one favorite and being loyal to them. We see respect - like when Maina gets on a train next to Eripiyo, who tells her with a smile that she will change "rooms".

There is so much charm about everything this story offers, in it's simplicity it's not only a great time-killer, and inside look into Japan's culture, but it's also a great piece of art.

Characters: 8/10
I talked a bit about some of the characters above. But there are some that should be mentioned. I want to start with saying that Oshi ga... does a great job giving every of it's character at least some kind of space and backstory.

I will only talk about a few of them.

Kumasa & Reo
Kumasa is an otaku, a good guy with huge heart. He is build bigger and presented as... not exactly a handsome man. But! The story never leans into it. It's such a nice thing, that he is not bullied or made fun of. He is accepted, and loved by his friends and Reo (the idol he loves the most).

He is a good person as well. Not a creep, but a respectful fan who promised Reo he would support her and make sure she became number one - but he never creeped over Reo.
Kumasa was also a great friend of Eripiyo. While he had no interest in Maina, he always told her what happened to Eripiyo, why she couldn't come and he tried to save her from a heartbreak with all he had.

Maki & Yumeri
I had to include them. These girls had the most beautiful, softest plot-story in the whole anime. They were so adorable, and their relationship was such a cherry on top. Everytime story focused on them, my heart fluttered and I was thanking gods.

What I'm saying is - you will get much more than what the story initially seems to offer.

Art & Animation: 6/10
This shows leans into realism as much as possible. Eripiyo is a regular woman (... okay, that might be a lie. She's basically a demigod, given what all she can handle), Kumasa looks a lot like otaku memes, and the idols vary in design & are kept on the natural side (with their hair color, for example).

It does not exactly stand out for it's artstyle, but it doesn't fall back either. It's very pleasant to look at - and the quality is also very decent.

As for animation, there is one specific thing that needs to be talked about. Oshi ga... does not use CGI for their dancing. Instead, it is animated by... well. I will try to sound polite. It's animated by a newbie.
The characters look off, the animation isn't on the smooth side, limbs have a tendency to look broken and their faces look lifeless.

Is it better than CGI? No. Not at all. Is it watchable? Barely.

Music: 6/10
For a music anime, Oshi ga... does not stand out, nor does it fall back. It's a good enough middle, where the songs aren't exactly memorable, nor is there too many of them (they tended to lean into one song a lot) but they ended up being nice.

Entertainment value:
9/10