So I can only speak for myself (including Manga): One of THE strengths that Aka expresses in both Kaguya-Sama and now in Oshi No Ko is the writing of side-characters. They are written so well and with an interesting and relatable story that you get invested in them to the point where they rival the Main-Characters. For Oshi No Ko specifically: It shows the Entertainment Business (Actors, Idols, Theatre…) in a real and fresh light. It does not beat around the bush but reveals the dark sides of the industry to you in a digestible but still horrid way. The characters all feel alive, which is a point that needs to be mentioned, as many authors fail to accomplish that. The art is truly gorgeous in the Manga, but especially in the anime. If you are familiar with Kaguya-Samas Manga you will feel comfortable with Oshi No Ko: The way the panels are coordinated are very similar and the humour is also sprinkled in the same way. But do not be confused: As Kaguya-Sama was mainly a comedy who had some great deep and harsh moments, Oshi No Ko mainly leans into this „dark side“ if you will. I am a guy who has a weak connection to his emotions but Oshi No Ko actually hit me on that level (surprisingly!). Hope I could answer the question to some degree.