it is ... that ..., precisely, in particular, definitely, for sure, only (when, after, because, etc.)
Noun +
The particle
Attaching
今年
This year for sure, I will study.
健康
It is health that is important.
When
Particle / Clause +
Reason Clause (から) +
Adding
忙しいから
It is precisely because I am busy that I use a notebook.
Verb て form +
Adding
部屋に入って
Only after entering the room did I notice.
When used with the conditional ~てはじめて (only after),