Krystal was someone Taemin considered to be one of his closest friends. Definitely out of F(x). Minho had Amber, he had Krystal. It was how it worked.

He wasn't there, but Jongin texted him when SM had flown him back to Korea from America to have dinner with Krystal and he couldn't help but feel angry. Jongin was his. Unfortunately, no one could know that, so he had to sit back as the man he loved paraded around with Krystal like SM's little rag doll, taking her to dinner and doing gentlemanly things he definitely should have been doing for Taemin instead.

So maybe he was a little jealous. He couldn't help it. He'd known Jongin since the younger was a trainee, way before EXO had debuted. He was jealous, yes, but he never intended to hurt Krystal. He was so invested in the idea of Jongin taking him for the first time in so long that he hadn't noticed her at first, but when he did he nearly shoved Jongin off of the bed. 

Krystal was a nice girl. Kind hearted. Patient. The kind of girl every boy wants. Except Jongin. He didn't want her at all, and he nearly cried because of the broken hearted look on her face.

Amber told Minho that Krystal had been waiting for Jongin to ask her out for almost half a year, but Taemin kept the stolen information to himself. After all, they only knew the happy side of the equation, unless Krystal spilled the beans to Amber. (It really wouldn't have surprised him if Amber came to the SHINee dorm looking to slit his throat after hearing the story.)

Jongin continued to 'date' Krystal afterwards, if only for the fans. Only Taemin knew that Jongin would come running back into his arms almost every night, peppering his face with kisses. Days Jongin spent out with Krystal always led to the best , no matter who was taking who. 

He almost felt guilty for how his nights ended when that's really what Krystal wanted, but at the same time, it had been a long time coming for other people to find out about them. Taemin was 95 percent sure that Kyungsoo already knew about them, plus Jonghyun was way too observant for his own good. So people knew. It wasn't something people made a spectacle of, so why would Krystal be any different?

Taemin couldn't do anything but pray that in the future, Krystal (as well as the world) would be able to give them their blessing so he could always be with the man he loved.