Was Touka actually serious or trolling about having sex with Kaneki?
Honestly, I might be wrong but I think there’s a little bit of both going on in that conversation? Just to premise this there’s 3 things I think we need to take into consideration when reading this scene
1) Touka is shit at delicately handling a conversation
2) She’s as subtle as a sledghammer
3) Based on Haise’s behaviour (“it was the same gaze you looked at Rize with”), she went into that conversation thinking Kaneki returned her feelings and wanted to find out if that was true
So re-reading that chapter with those things in mind, this is my interpretation
Are you finding it hard to confront me because you’re inexperienced with dating/girls? It that the reason why you’re pushing me away now? I thought perhaps our relationship had been going somewhere but you keep leaving me behind.
When you’re ready, I want to take that next step in our relationship
So I don’t think she was joking- she really would have sex with Kaneki. But at the same time she was joking, you get me? I don’t think she was saying it to actually try and proposition Kaneki right then and there. She’s just…. not good with words.
Then comes the part where she’s trolling and for this, I agree with @ishida-why‘s comments and explanation here [x] about this scene:
Paraphrasing from her a bit:
Kaneki misunderstands her and thinks the reason Touka said she’d let him “do it” with her was to stop him from going away.
Touka messes with him and jokes “trying to do what?”
Realising that Kaneki is as oblivious and dense as a brick, she decides to spell it out for him and brings out receipts from Haise’s puppy dog crush
Then she confesses, saying she was happy to be looked at like that
Cue light bulb above Kaneki’s head:
This is basically his “holy shit this is a confession” face