Shizuka is... alright. Truth be told, if I could dodge her as an LI, I probably would. The payoff for the build-up will likely be worth it, but that is not where my issue is.
If I want cute or sweet, there is stuff I can do that doesn't involve porn that will fulfill that. I would even prefer that, since blending porn with fluffy/sweet to the degree of Shizuka's content kind of weirds me out. It hits the same notes as pigtails or an excessively pink or heart-themed room.
If it were not for the medium she's in, the stammer plus the circumstances we meet her under mark her in my head as someone to be defended and left out of the bedroom. This being very much a porn game, though, she only just manages to get over that hurdle. But only just.