Touki

Karin needs to be herself and do what she wants to do. She is so talented and charismatic that the worst thing she can do is follow the bored solo-style UFA has. She has to do the music she want and be the funny crazy bitch she is. That's all.

Only if there is a company that is willing to invest in her. In UFP it's safe but she won't advance much, but outside UFP she has to govern her own problems (from singing, choreography to finding appropriate music label, managing own budget). Both choices have their own advantages and disadvantages. Let's wait and see how Riho did outside of H!P first. However, I believe that Karin's fanbase is stable and won't decrease much after she leaves, which is an advantage for her. Every success has its own hardship, though.

It's been a long time since I saw that facial expression. I know that her facial expression is good, but this is beyond what I expected. Also, she usually shows her more cheerful side, but now she amplifies the sadness of the song excellently.

MM's career seems to have 2 peaks and 1 dip, as you guys mentioned. 1 peak during Golden Era, and around 2000, another lower peak during Colorful Era, around 2014 - 2015, and a dip during Platinum Era (even when the mass leaving of members occurred in 2004 - 2005, the dip was due to the leaving of all Golden Era members). In K-pop, there's a rumor of "7-year curse", but in J-pop, the rumor is "5-year curse" instead. Kobushi disbanded 5 years after debut, Country Girls also around that period. However, I don't know about the past. Also, while people perceive scandal as a stepping stone to idol careers, I think in H!P, members used scandals to get out of the office ASAP. I predict that Yaguchi-san and Fujimoto-san did that because they were fed up with the current line-up and the treatment of managers. Tagucchi and Renako of Kobushi Factory also used scandals to get out of the group while their contracts hadn't expired yet. I cannot give any conclusions regarding mass leaving of members in 2004 - 2005, since members are from different gens and joined the group at different times. 

I must be looking at the mix between Chayu and Airi.

I don't think I'd ever stop being excited whenever Tsubaki performs. DanshaISM has solo lines almost equally distributed, since you'll never see Rikoriko and Ami get that many lines. Ima Nanji is "Goddess", the expressions of every member are extremely charming and fit the song really well.