彼は深刻な顔をして部屋に入ってきた。
He came into the room with a grave look on his face.
そんなに深刻に考えなくてもいいよ。
You don't have to take it so seriously.
彼女は進路のことで深刻に悩んでいる。
She is deeply troubled about her future course.
二人は深刻な様子で何か話し合っていた。
The two of them were discussing something with a solemn air.