@Ezralva
Okay, as you have read in the latest chapter (c24) you can see that both Ying Feng and Ling Xiao is in training camp, on the last day of the camp, all students need to enter a cave and kill monster, there are Level A, B, C etc(can't remember) but the training coach say that there aren't many level A, not to mention Level S or SS monsters, but Ying Feng and Ling Xiao accidentally meet level SS I think, or level S, both of them can't handle that monster and Ling Xiao injury is more serious compared to Ying Feng,
When they both can't run anymore and gonna die, Ying Feng push Ling Xiao aside and tell him to run away. but ling xiao didn't run, he injects himself with ember v2, after ling xiao defeated the monster, he when into estrus, he tried to attack Ying Feng but Ying Feng is still rational that time, Ying Feng inject himself with antidote for estrus (the one that the weak guy change, it wasn't an antidote but a liquid that triggers estrus), thus both of them can't control themselves. Ying Feng win (well, Ling Xiao injury was bad b4he even inject himself with ember, then he fight that monster = more injury..poor him.)
Then both of them are bonded.
Q: Desn't that need special setup of bridal chamber?
A: Nope, they don't need that, as long as both of them were in heat/rut, they can do this ceremony anywhere since this ceremony is to kill each other, so the place doesn't matter, but to ensure both of them are alive after the ceremony, school will prepare place for the ceremony,so that they can give medical attention as soon as possible to both of them.
Q:don't they need to register themselves as couple beforehand?
A: usually they need to do that, i mean formally, but LingXiao and Ying Feng didn't register as they accidentally do the ceremony.
Q: What is a blood contract and what does the contract ensue for the both of them?
A: I can't remember about blood contract, but if you are talking about Qizhu, Qizi contract, then I can explain. You have 2 nestlings that already matured, these matured nestlings have sexual urges. So, when both of these nestlings in bridal chamber, instead of making love, they will try to kill each other, as for why they did that, it was their instinct, they somehow know that they can't afford to lose, so they fight to the death with each other, they even can't remember with whom they fighting. they also know, to win, they need to dig the other person heart, after that, the one who win became Qi Zhu, loser became Qizi.
This contract will be automatically installed (?) inside them. after they finish with the ceremony, Qizhu will grow stronger while Qizi will grow according to Qi Zhu's taste, so there might be wrestling-type of uke, (because its according to Qi Zhu fetish.) Qizi also will have a psychological need, that is he needs to be around Qi Zhu all the time (for the first week after the ceremony) or else this Qizi gonna have a head trauma(forgot the term) for all his life.
Q:How did they accidentally do the blood contract if Ling Xiao was unconscious?
Ling Xiao wasnt unconscius when they were doing the ceremony, he faint after that.
Hope this is clear, and sorry if there's any mistake , I use MTL to read this novel