The real way for Vecna to use Will’s love for Mike against him wouldn’t have been to somehow out Will before he got to come out on his own terms. What he needed to do was take Mike hostage. Like Will breaks into Vecna’s mind, sharing that space, and suddenly he sees Mike. He sees Mike and he’s in Vecna’s head and he knows what Vecna plans to do, how he intends to hurt Mike.
And then it becomes a save the world/save your lover decision for Will. And Will— Will hesitates. He thinks about it for far longer than he should. And then he picks Mike. He refuses to follow through on the predetermined plan until he knows Mike is safe.
Will puts the world in jeopardy, he pushes everything to the absolute brink. We get Will bargaining to trade himself for Mike, we get him risking bodily harm to try and get to Mike before it’s too late.
And I don’t mean that this is one of Vecna’s visions, messing with Will. I mean that he literally takes Mike captive like he did with the kids. And everyone is begging Will to continue with the plan, promising that Mike will be safe once Vecna is killed and that they will rescue him when they rescue all the kids. But Will can’t and won’t risk it.
His actions alone out him here. Vecna put him in a position where his heart is bleeding openly on his sleeve and there’s no mistaking his desperation and fear.
But as a bonus, we can have a scene where someone is telling Will that they still have to follow the plan, it’s all figured out, and why does he care so much anyway?
And Will, nerves frayed, just snaps “because I love him!”
And sure, it’s not how he meant to ever confess that, if he was ever going to confess it anyway. But anyone who hadn’t figured out that he was in love with Mike in the last five-or-so years had definitely figured it out in the last five-or-so hours. He knows that it’s obvious, that everyone is looking at him with those expressions because they’re all watching his heart shatter in real time.
And really, what does the confession matter? The current situation is that the world ends, Mike dies, or Will dies. And in the face of that, putting words to his love of his best feels both empowering and somehow kind of insignificant. But in a way that’s freeing. A way that means his love isn’t the end of the world, it won’t define him negatively. Instead it will define him as someone willing to give up everything for love, someone willing to sacrifice for it.
In the end, of course, they both survive. And Will has no intention of confessing to Mike’s face. At least not now, not after everything. But how desperately he hugs Mike, how closely he clings to him certainly hints towards it. And when Mike wakes up to find Will, bloodied and clearly having gone through hell, he hugs back just as hard. He realizes that he just almost died and that Will gave everything he had to save him. And those are the only realizations he has the time for right now— the rest can wait until after they do save the world— but that’s enough for him to cradle the back of Will’s head gently while they hug, enough to have him assessing Will’s injuries and fussing over him.
(Later the party tells him about Will, about how panicked and afraid he was, about his borderline suicidal plan to save Mike. They don’t tell Mike about the confession directly— that needs to come from Will and they love and respect him too much to take that from him— but it’s just as obvious in their retelling as it was when they were experiencing it.
Mike doesn’t ask Will later, not directly. Because he knows. He’s always known, even if he didn’t give it conscious thought. Instead, he just shows up at Will’s house unannounced. And when Will answers, still a little bruised and banged up, radiating the nervousness that Mike expected now that everything was over, Mike is overcome with so much love for Will that he just tugs him into a kiss. And then Will melts into him, kissing him back. The figuring things out comes later, but they do it. And they do it together. Forever,)