イナズマジャパンが世界一となって１０年。
I am playing イナズマイレブンＧＯ, and I ran into this line. From just the words, I am guessing it means something like "It has been 10 years since Inazuma Japan became number 1 in the world". However, I'm not sure how to break it down grammatically.
My question basically boils down to 2 things:
It means exactly what you said; there are two useful grammar points here to break down:
The first is the te-form followed by a temporal durational adverb. This essentially always means “It has been <durational adverb> since <completion of verb before it>.” For instance “東京に来て二週間、まだ友達ができていない。” for “It has been two weeks since I came to Tokyo and I still haven't made any friends.”. One can also sometimes see this with “で” after the adverb, which would simply make it the conjunctive form of “東京に来て二週間だ。”, which means “It has been two weeks since I came to Tokyo.”. It's important to note that this “〜て” pattern is very often followed by a sentence after it directly. Using “〜で” explicitly comparatively rare. But it can also be a standalone sentence with nothing following it, like here. One may also opt for other translation styles such as “I still haven't made any friends two weeks after coming to Tokyo.” for instance which one could argue is a more idiomatic translation.
The second part is “〜となる”. This is synonymous with “〜になる” which you probably already know, but is more formal and literary. “〜とする” can also be used instead of “〜にする”.
Adding those two up, we arrive at your proposed translation.
P.s.: Actually, being reminded of this due to something I read “completion” of the action isn't quite the right term, it's more so the same nuance as the “resultant state” of the verb with “〜ている” which may be completion, in many verbs, but for instance “付き合って二年の人” means “Someone I've been going out with for two years.”, not “Someone for whom it has been 2 years since I've been going out with him.”, likewise the real example “お風呂に入って何分で 1℃体温が上がると思う？” of course means “How many minutes must one be having a bath for one's body temperature to rise by one degree centigrade do you think?”, not “How many minutes must it have been since one had a bath for...” of course. “来て二週間だ” definitely means “It's been two weeks after I came.” however, not, “I've been coming for two weeks.”
