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main topic; main subject; main issue; main question
this subject
前置きは省いて本題に入ろう。
Let's skip the preamble and get to the main topic.
そろそろ本題に戻りたい。
I'd like to return to the main subject soon.
話が脱線していたが、ようやく本題に辿り着いた。
The conversation had strayed, but we finally got to the main point.