Reason

"Lan Zhan. Lan Zhan." Wei Wuxian called Lan Wangji one afternoon Lan Wangji visited his wife in Yunmeng.

"Hm?" Lan Wangji said, his eyes never once left Wei Wuxian's face.

Wei Wuxian smiled, which made Lan Wangji's heart skipped a beat – though you wouldn't find even a slight trace of this.

"I want to ask something!" Wei Wuxian said.

"That is?" Lan Wangji asked, still staring at every angle of Wei Wuxian's face.

Wei Wuxian, shameless as he is, just let his husband do as he wanted. "Why is ZeWu-Jun always smiling?" he asked.

"I don't know." Lan Wangji honestly answered.

"But, but – " Wei Wuxian said. " – there was a time he seemed to stop smiling, right?" he asked. "That time when..." he said, his voice trailed off.

The air suddenly seemed colder. Lan Wangji's gaze froze on Wei Wuxian's face. His embrace on Wei Wuxian became tighter, though still gentle.

"I'm sorry, Lan Zhan." Wei Wuxian said, his head hung low. After all, around that time he died.

Lan Wangji's heart is still very bitter of it. But, nonetheless, he answered – for the sake of his wife not to do a self-blame. "Brother (LXC) always smiles not to make others worry." He said. "Maybe that's why brother resumed smiling." He explained.

"Oh!" Wei Wuxian said, he bumped the side of his fist on his other hand's palm.

The two continued to talk, obviously avoiding the matter. But, to the bystander and silently listening Jiang Cheng, his face is fully covered in dark lines.

Why? It's because he exactly knew what happened why that person resumed smiling. It's because of 'that'.

Should I - ? he thought, hesitating. In order to bring back the smile of this person – the one who saved him during those times he was down – like what this person is now.

Out of impulse, Jiang Cheng's stiff facial muscles moved.

Lan Xichen's eyes went wide. "Ah – " he said.

Jiang Cheng's eyebrows are tightly knit, his eyes squinting. His cheekbones can be vividly seen on his cheeks as his lips are outstretched, showing his pearly white teeth that's tightly gritted.

Jiang Cheng's eyes moved and he blinked, seeing Lan Xichen's unreadable expression as he stared at his face.

"What?" he asked after he fixed his face. It's back to 'normal' (blank) now.

"That's..." Lan Xichen slowly said, pointed at Jiang Cheng's face.

Jiang Cheng nodded. "Yes." He said. "My smile." He told him.

Lan Xichen's face froze blankly before it finally broke. "Pft – " he said and covered his mouth, his shoulder slightly shaking. "Ahahahahahahaha!" he laughed, his shoulder now violently shaking as he held his stomach. "Ahahahahaha! Ahahahahahaha - !" he laughed, tears on the corners of his eyes.

Jiang Cheng's forehead knotted. "W-what?" he asked, confused. "Why're you laughing?" he asked him, puzzled.

Lan Xichen is having fits, and so Jiang Cheng patiently waited for him to calm down.

"No, no..." Lan Xichen said, still laughing. He almost choked for suppressing a laugh. "Sect Leader Jiang, you – " he said, then covered his mouth to laugh again.

This time, Jiang Cheng frowned. "What?" he asked, starting to get pissed. "What are you laughing about?" he asked.

Lan Xichen stopped and stared at him. Finally, he smiled. Jiang Cheng's eyes went wide.

"Sect Leader Jiang." Lan Xichen called, his voice soft.

"What?" Jiang Cheng asked.

Lan Xichen smiled wider, then slightly lowered his head. "Thank you." He told him, then turned away.

"Huh?" Jiang Cheng said, puzzled.

But, Lan Xichen already left.

Only days later had he realized what happened. Yes. 'days'.

He covered his face with his both hands and rubbed them. Aaargh! How embarrassing! He thought, his face red. He finally realized why Lan Xichen laughed at him when he looked in the mirror and tried to imitate the person's smile.

I looked like the worst fierce corpse! He thought, his face so red it looked like it's about to explode.

"Huh? What happened to you, Jiang Cheng?" Wei Wuxian asked when he and Lan Wangi saw him tossing and turning on his seat on the corner.

"Stomachache?" Lan Wangji asked.

Hell no! Jiang Cheng thought. But, he can't refute since he's so embarrassed. "Yeah – " he just grunted as he doubled over.

He just buried his burning red face and kept silent the whole day.