he is emotional because she is probably the first person he has ever been able to relate to, giving us this oral sex:
“you’re not alone.”
“neither are you.”
rey says she goes into the cave hoping to find answers. she entered the darkness hoping to find clarity in her confusion.
ben solo was failed by his master, his uncle, before deciding what side of the force fence he lies on.
ben turns to snoke to find clarity and purpose, believing his choice was made. he turns to the darkness hoping to find clarity in where his destiny lies.
the darkness leaves them both feeling alone and confused.
i think the force touch scene makes them realize that they both have similar problems with intertwined solutions. However, they only see it in their own way because, for right now, it’s all they know. it’s their only clarity.
this doesn’t mean that they can’t find this clarity together.