Encircle

From the prompt:
In his defense, Xiao Zhan was very hard not to love. From the day Yibo had first arrived at the institute, orphaned and afraid, the two of them had gotten along like two halves of a whole, eventually becoming sworn brothers as close as blood. Hunting demons was a dangerous business and hunting as bonded pairs greatly increased efficiency and survival rates. But finding another soul you had such high chemistry with to bind together mind and soul was a truly rare occurrence. That was why Xiao Zhan and Wang Yibo's astronomically high compatibility potential was such a miracle.There was just one...small...problem. Amongst bonded pairs, romantic relationships were completely and utterly taboo. From AO3 reader Biscutpoo