Need a little help with a sentence.

[Kaia]

秋になると、両リーグを通しての日本一を決める試合が行われる。

It looks like it means that when autumn comes, the best Japanese team is determined in a game. (The two leagues here are the pacific and the central league it says, I know nothing about baseball.)

1. What does 通す mean here? I thought it was just the intransitive version of 通る.
2. Why does の appear after 通して? Are verbs in て-form nouns?

Thanks in advance!

 

[Elizabeth]

秋になると、両リーグを通しての日本一を決める試合が行われる。

It looks like it means that when autumn comes, the best Japanese team is determined in a game. (The two leagues here are the pacific and the central league it says, I know nothing about baseball.)

1. What does 通す mean here? I thought it was just the intransitive version of 通る.
2. Why does の appear after 通して? Are verbs in て-form nouns?

通しての is kind of an example of a phrasal verb ?? in Japanese which in English refers to a verb connected to a preposition or adverb. It is a nominalizer, but I believe the meaning is still 通す. A game that is decided "through" or "by way of" the two leagues.

Sorry this isn't more help. lol. I just always read it like a noun without bothering to ask the hard questions later.

 

[undrentide]

秋になると、両リーグを通しての日本一を決める試合が行われる。

It looks like it means that when autumn comes, the best Japanese team is determined in a game. (The two leagues here are the pacific and the central league it says, I know nothing about baseball.)

1. What does 通す mean here? I thought it was just the intransitive version of 通る.
2. Why does の appear after 通して? Are verbs in て-form nouns?

通して（＜通す） here means "through". As you mentioned there are two leagues and they usually play separately. の is used to modify 日本一 with 両リーグを通して.
When autumn comes, they have a game to decide the No.1 in Japan through both leagues.