I am almost 80% - 90% sure that this is from the 
episode where Kikyo straps Kagome to a tree with 
her soul stealers and attempts to drag Inuyasha 
into hell with her.  This is right before the 
hole opens up and they kiss (And Kagome sees 
it!). Sorry, I don't know episode numbers but I 
think it's second season!  >_<

If it's not that one (although I'm almost 
positive it is), then it's the one where Naraku 
chases Kikyo with his poison insects/giant hairy 
monster and she runs into Inuyasha who saves her 
and tries to express feelings etc and she laughs 
at him. Then Inuyasha realizes he will always 
love Kikyo etc. and Kagome has to come to terms 
drama drama drama (Third season maybe...this is 
what I get for watching stuff out of sequence!)

Hope this helps! o_O