freeradical9

I think the Sanzo/Hakkai thing is not just simple gratitude, but flat out obligation, service and knowledge of an unpayable debt. Gojyo saved his physical life, but Sanzo in arguing his case before the Sanbutshin has given him a chance at redeeming his soul. And with Sanzo as sort of his spiritual parole officer, more or less, there's a hierarchical relationship that you don't have with the debt of gratitude towards Gojyo. They're bound together by a higher authority, while the association with Gojyo is just a personal matter that could be ended at will. It's very telling that Sanzo used the talk of a classical "bite off his tongue" suicide to express the depths of Hakkai's loyalty -- it couches the relationship in a rather feudal air which makes the serious depth of it all very apparent.