I like Satonaka more for her position than her admittedly weak character arc.
But here’s the thing about Satonaka’s character arc — it’s not necessary for it to be big or dramatic. Satonaka isn’t someone who needs to grow as a person. This story isn’t about her. Not every character is going to have a dramatic arc of growth like Ankh or Gotou’s.
The shine on Satonaka’s character comes from the fact that she’s a woman in a very strong position. She’s the voice of reason and calm to Kougami, Gotou, and Date. If this show was Kamen Rider Birth and not Kamen Rider OOOs, she would be in the Akiko/Hina/Yuki position. She basically is in that position for that area of the cast.
Satonaka doesn’t take shit. She does her job quickly, efficiently, and to the best of her ability even if she doesn’t always want to (she admittedly doesn’t like sweets very much but she will eat that fucking cake because that’s what she’s paid to do) but if someone gets in her way, even if it’s her employer or her friends, she won’t just roll over for them. If she thinks they’re wrong, or that they need someone to smack them upside the head and tell them to get their shit together, she’s going to do it. She may come across as kind of cold, but she does care about all of these crazy motherfuckers in her life, especially Gotou. But she just shows it in subtle ways, because she already has to deal with Kougami being dependent on her, and she expects better from Gotou.
Satonaka has no motivation to grow as a person. She’s not being challenged by anything directly. Satonaka Erika is exactly who she needs to be to get done what needs getting done in her life. The fact that she’s so set and sure of herself, especially in such a chaotic environment, is part of what makes her so great.
You’re free to like, not like, or dislike her as you will. I’m not saying you have to think she’s great or that she has to be your favorite character. I just thought I’d explain why I love her so much. OOPS I DID THE THING AGAIN SHIT I’M SORRY I CAN’T HELP IT I LOVE CHARACTER ANALYSIS.