Is there a word for this opposite reaction you can have when you meet someone after a long time?

Question

These are the feelings/emotion I would like to describe with a word:

You have been really a close friend of another person for many many years, and then you stopped hanging out together and even calling at telephone. Then you suddenly met at a party. You manage do to only small talk and nobody knows really what to say. There's a general embarrassment and you end up without speaking too much.

The opposite situation is when you meet at a party somebody who you weren't in touch with for so long, and both are more than happy to met, and it is as only a few days have passed since the last time.

How would you name these stuff?

Answer 1

For the first situation:

"We no longer had anything in common."

"We had become strangers."

For the second: "We just picked up where we left off."

The first is an "awkward interaction."

The other is a "happy reunion."

Answer 2

I'm sure someone will eventually have one but I don't have one word for it. Until then, please consider what I use and think I made up. It is self-explanatory.

A tributary or affluent is

a stream or river that flows into a larger stream or main stem (or parent) river or a lake. For this to happen, the break apart or part ways at some point.

A confluence is

the flowing together of two or more streams

the place of meeting of two streams

the combined stream formed by conjunction.

One could say, "the confluence of two affluents/tributaries, " "they are affluents/tributaries at a confluence" or "affluents/tributaries in a confluence."

It would try to delineate that two friends(two streams) parted ways long ago but are now reunited (a confluence) in a way that is remarkable because after the confluence you can't tell the two streams apart. It's as if they never steered away