Why was he holding his hand (when he's supposed to be mine?)

Chapter 17 - I keep on Crying -

They had agreed that Mike would head over early to set up the basement that way Lucas could take everyone else later and Max could just relax. Max looked at Will then said in a hushed voice so the others couldn't hear. "You should go with Mike." Will just shook his head at her. "I don't know if it's a good idea Max." Then she shook her head at him. "He's your best friend Will. You have to sort it out." Will still looked at her hesitation obvious on his face. "Mike!" Max called out. "Will's gonna go with you."
Rolling his eyes Will walked out the door with Mike. The awkward tension entered the air again.
"I miss you." Mike said, eyes wide and hopeful. He was grateful for Max for smacking some sense into him (literally). Will was his best friend, though from what Max had implied maybe Will had wanted to be mo.... nope. Mike shook those thoughts away; he was fine with Will being gay, but he wasn't. He liked girls.
"What do you mean?" Will asked. Brown eyes full of hope as well.
"I know I say I'm your best friend, but we've felt like strangers lately. Even before David. I miss having my best friend around Y'know?"
Will nodded smiling. "Yeah, I get it." Silently Will cursed himself. Wasn't he supposed to make it hard for Mike this time? Wasn't Mike supposed to change before Will blindly forgave him? He scolded himself. Mike's apology had been real. It was fine. They were fine.

As they drove to Mike's house Will realized how long the drive was going to be. The Wheelers house was on the other side of town. Meaning they would have to drive through rush hour to get there. They were gonna be in the car for at least 30 minutes. So they would also have barely any time to set up for the others. Meaning there was no point in being alone together in the car anyways. Thanks a lot Max, he thought to himself.

Those where the thoughts Will was obsessing over until he heard thunder. He gasped and began to feel his body go into overdrive. Not able to slow his breathing as lightning now appeared in the sky he started to gasp for breath. What had Dr. Owens told him? In through the nose out through the...oh God. The rain was bad, but thunder and lightning were worse. Sometime the episodes were okay, just trouble breathing, but this time he wasn't so lucky. Sometimes it was like he was back there in the upside down. Hearing the demogorgon's breathing, trying to run for his life but often it was like his feet were glued to the ground. He was forced to stand there while he was eviscerated by the Demogorgon.
Mike hadn't even noticed the sky darkening, hadn't been bothered by the rain until he had to turn on his wipers. The first sound of thunder had made him jump a little, but that wasn't what scared him. What scared him was Will who suddenly seemed to be having trouble breathing.
Of course. Mike was such an idiot.
He pulled off the road and into a small, abandoned parking lot.
"Will, hey Will."
"Come on Will snap out of it."
He stared helplessly at the other boy convulsing in the passenger seat. He had to at least stop him from doing that. He wrapped his scrawny arms around Will's body and pressed him firmly to his chest.
"Come on Will you're gonna be okay." Will's shaking slowed a bit.
"Deep breaths that's all you gotta do okay. In and Out, In and out."
He did the proper breathing techniques and finally heard Will calming down and doing the same.
Will heard Mike's voice, finally. He was able to snap out of it. He was about to reach up to wipe the tears of his face when he realized Mike was holding him. Mike had moved over to the passenger seat. Sat Will in his lap and was holding him. He felt electric. Every part of his body Mike was touching felt like it was on fire. He was sure his face was bright red.
"Mike, you didn't have to do that."
Mike adjusted his body, letting go of Will. It felt strange now that Will was present in the moment.
"Course I did Will. You were having a panic attack. I had to help you." Will smiled trying to hide the worry on his face. This hadn't felt like a panic attack, it was something worse. Still, he was grateful for Mike. Another bolt of thunder and Will cringed.
Mike crawled awkwardly back over to the driver's seat and started the car back up.
"You gonna be, okay?"
The concern in his eyes made Will melt. He tried to play it cool and shrug his shoulders.
Mike started to drive but then decided to do something he hadn't done since they were kids. He put his right hand around Will's shoulder. He had decided to change right? To be a better friend, and Will needed comfort right now.
The only confirmation he needs to know that it was okay was Will's shy smile looking back at him.