Is seduction immoral? One reason for thinking it ethically problematic is that it seems to be essentially manipulative: the seducer seeks to entice the target into acting against their better judgment. They are thus treated as a mere means, which disrespects their autonomy/agency. (The problem generalizes to any form of non-rational persuasion, whereby one attempts to shape others' ends or get them to do what they normally wouldn't.)
On the other hand, there is Mary Coughlan singing, "I want to be seduced..." If the experience is fun or gratifying, it may be an instance of merely 'local' irrationality that can fit unproblematically within one's larger life plan. And then it's not really disrespectful at all: the seducer is acting in line with the ultimate ends of their target. So we're left with the somewhat trite conclusion that whether it's okay to treat someone a certain way simply depends on whether they want to be so treated. Hmph.
So here's a more interesting question: what should one do if the other's desires are unknown? What should the default assumption be? (Asking is not always a neutral option -- cf. "would you like a surprise birthday party?") I suppose as long as you recognize that the other person's ends matter - even if you're not yet entirely sure what they are - then you probably can't go too far wrong. But I'd be curious to hear what others make of the whole issue.