이건 ○○ 레슨 ○○하기

This is the ○○th Lesson: ○○

This meme began to gain significant popularity around July 2025. It originated from the lyrics of 'Thank U,' the title track of U-Know Yunho's 2nd mini-album 'NOIR,' released on January 18, 2021. It spread rapidly through social media algorithms, especially after streamer Looksam covered the music video. It gained immense popularity through short-form video content like Instagram Reels and YouTube Shorts, even leading to a resurgence on music charts.

The meme "This is the ○○th Lesson: ○○" originated from the unique expressions in U-Know Yunho's song 'Thank U' lyrics: "This is the first lesson: keep good things to yourself; now, the second lesson: bear your sorrows alone; finally, the third lesson: don't be swayed by joy or sorrow." This meme is used to seriously deliver one's own 'lessons' or 'tips' about a situation or action, much like U-Know Yunho. The original song's serious yet somewhat exaggerated atmosphere, combined with U-Know Yunho's 'passionate' image, creates humor. The fact that only the first and second lessons appear in the first verse, while only the third lesson appears in the second verse, sparking curiosity about a 'fourth lesson,' also contributed to the meme's spread.

It is actively used primarily among young internet users aged 10 to 30, K-POP fandoms, and especially U-Know Yunho's fans. Those who frequently consume short-form video content make up the majority, and it is also widely consumed by all age groups interested in sharing humorous and relatable 'life lessons.'

• "This is the first lesson: work moderately before vacation."
• "This is the first lesson: keep good things to yourself."
• "This is the first lesson: listen when spoken to nicely."
• "This is the first lesson: get notifications from the National Secretary."
• "This is the first lesson: don't be late."
• "This is the second lesson: resist late-night snacks."

The Korean phrase "이건 ○○ 레슨 ○○하기" is pronounced as "Ee-gun [number] Leh-seun [action] Hah-gee."