I notice a bit of discussion about this over here. I think @Blue Of Mind made a reasonable guess:Since we’re on the subject of Wat and the VB’s he posted this uhh “interesting” tweet a few days ago Apparently this is the TL and deepL seems to match up with it a bit but of course if there’s anyone who can provide us a better or more accurate TL it’s appreciated. Either way looking forward to seeing what he’s talking about, Kaito NT?
When I heard about it, what occurred to me is that, at least in English, the word "sexy" has been appropriated into a bunch of other things, even if they're not sexual in nature. Cars can be sexy. Parts of music or songs as a whole can be sexy. Sexy has come to mean basically anything of unexpected and uncommon quality. Although the thing seems to need a certain "cool" or "rare" factor to be called "sexy," too--like it has to be cool itself, or in some way exclusive. For example, I doubt anyone has called a great house "sexy," but they would refer to an appealingly-designed automobile as such. Some linguist or sociologist who's given it more thought could probably explain it better.I think Wat wants to make Kaito NT sound more smoother and "sultry" compared to previous Vocaloid versions?
Anyway, that ramble aside, I think Kaito's voice could be described in either context--either a desire for it to be more sultry, or simply become more sexy in the "awesome" sense.
Or, you know, people have had various issues with Kaito's voice, comparing it to bagpipes or other things. Fixing those things would seem to automatically make it more sexy/maybe erotic in the traditional sense. Though I'm sure there are any number of people who like Kaito's voice as it is.