쓰는 건

using

→ 쓰다
phrase Rare #20,099
using 쓰다 can mean “use” or “write,” depending on the object. 건 is a shortened form of 것은, which marks the action as the topic.
KO: 이 앱을 쓰는 건 정말 편해요.
EN: Using this app is really convenient.

쓰는 건 좋은데, 불 잘 꺼

It’s nice to use, but the battery runs out quickly.

— 반딧불의 묘 (1988)