As for "the context", yes and no. They are talking about a robot and monsters, and there are robots and monsters who can use a sword, generally speaking. I don't think it has something to do with your translation "the fellow who uses the sword is a robot / or / a monster exists".
I understand all the texts but the idea of all the passage is zero.
The context is:
those pilots and the father of one of them being caught in a spell. The father turns into a dog and the remaining 3 kids will turn into a dog too if they let their true identities revealed. Now they have to think of a plan to avoid being questioned by the other allies.
I presumed the "gambar" team was some in-universe reference?
仲間 is not "friendship". They will pretend to be 虎太郎's friends, and "忍者仲間" is the answer to "どういうつながりの友達?" (つながり : how they are friends, what connection, etc)
くすぶる【燻る】
1 〔発展・活動しない〕
彼は下積みでくすぶっている
He is still an obscure underling.／He is getting nowhere.
しばらく田舎でくすぶっていた
He stayed in the country doing nothing for some time.
一日中家にくすぶっていてはだめだ
You shouldn't stay indoors [at home] all day long looking so glum.