Orochimaru wanted to ask Uchiha Yi for some blood so he could study Sage Mode, but after thinking it over, he abandoned the idea.
Besides mastering Sage Mode, Uchiha Yi was an Uchiha. Asking a ninja with a bloodline ability for his blood out of the blue would be terribly presumptuous. There were even techniques in the Shinobi World that could curse someone using their blood.
A ninja's blood and cells both held information about them.
Forget Uchiha Yi. If someone asked Orochimaru for his blood, he would refuse—and might turn on them outright.
Orochimaru considered himself close to Uchiha Yi, but not close enough to openly ask for his blood.
If their positions were reversed, he certainly would not give it to him.
"I plan to study Sage Mode later. Sorry for the trouble, but I'd appreciate your help," Orochimaru said. After a pause, he added, "Of course, if there's anything you need from me in return, just say the word."
"I usually have plenty of free time, but studying Sage Mode really is difficult. One mistake could kill you.
"Of course, I can help you avoid the danger of Natural Energy backfiring, but I'd have to watch you the entire time." Uchiha Yi did not refuse. He understood what Orochimaru meant, and the two exchanged a knowing smile.
This would be no small favor to owe. At the very least, Orochimaru would have a hard time refusing if Uchiha Yi asked him to do something in the future.
The Orochimaru of today, at least, could not refuse. Uchiha Yi did not mind working with him, either. This was not the Orochimaru of later years; he still had his humanity.
Besides, even when Orochimaru eventually went astray and tried to take Sasuke Uchiha's body, all he managed to do