I think people are forgetting Shizuka has only been around MC for about 2 months or so at this point and was completely innocent to start beyond what could maybe described as a crush on MC. We have had much longer to know these characters that what they would themselves due to the time between updates, for the two odd weeks we wait they progress a few days only. [To be clear not knocking update time or anything like that, just trying to state facts]She's not really that innocent, in the belly rub scene of the latest update, she makes it clear when they talk about the lesbian porn movie they are watching. When she tells MC that she isn't interested in women, but gets horny when watching that movie because she is constantly imagining MC doing those things to her.
It was only 3-4 updates ago (Christmas in game) where Shizuka was upfront with MC but that was also when she was drunk.
It is kinda like watching her trying to speed run becoming a full on deviant.
We have known the innocent Shizuka much longer, I mean even in this update the innocence is played upon when she wants to help clean Zeus.
I would need to go back and play the content again but I think this is the first time she was upfront while sober what she is wanting with MC, sure they have played around before but I'm pretty sure MC was playing that off as Shizuka learning about her sexuality.
Personally I'm still seeing her as the innocent curious Shizuka stage, the sexual push is quite a step which I can attribute to the events of Christmas but am still trying to wrap my head around the change in Shizuka. [Not saying it's wrong, just quite fast IMO]