What are the fundamental differences between the ～と一緒に and the ～とともに fragments?

Question

I'm accustomed to saying `together with` using the `~ to issho ni` fragment, but I've been noticing that some people I talk to phrase this using `~ totomo ni` instead. i.e. 彼女と一緒に日本へ来た。 Kanojo to issho ni Nihon e kita. and 彼女とともに日本へきた。 Kanojo totomo ni Nihon e kita. seem to be fundamentally equivalent. Are there any nuances that the two have that dictates when and where they should be used? Probably very slight meaning deviations? Or are they essentially perfect equivalents of each other when it comes to saying `together with` (and yeah, I'm aware that `~ totomo ni` has other meanings aside from that)?

Answer 1

TO TOMO NI is used to express the idea that two things share a common property(A) or do the same thing together (B), take place at the same time (C) or a single entity possesses two properties (D).

A) Sutainbekku wa Hemingywei to tomoni Amerika no daihyouteki sakka no hitori da. - Steinbeck, along with Hemingway, is representative of American writers.

B) Watashi wa shokubanodouryoutachi to issho ni sono demo ni sanka shita. - I took part in a demonstration with my colleges from work.

C) Byouki ga kaifuku suru to tomo ni shokuyoku mo detekita. - As I recovered from my illness, my appetite came back.

D) Kare wa kagakusha dearu to tomo ni tekugakusha demo atta. - He was a scientist as well as a philosopher.

In B, it can be replaced with TO ISSHO NI, but the phrasing becomes more colloquial.

The other functions of TO TOMO NI can be replaced with other phrases as well.