Boy Next Door's Rio left a cute photo of Seongho and a touching letter

KOZ's number one, our Seongho~
Having always talked a lot since way back,
I always lived a proper life, pushing my fellow trainees hard and getting on their bad side along with them. I couldn't remain just a good older brother, but because of those times, I think we can still quickly catch and correct any parts we might be missing or areas where we are falling apart. The current Seongho may not understand or like the Seongho of those days, but that is Seongho, and he is still Seongho.
I think all those sides of you ultimately made you the perfectionist and meticulous person you are today haha. Keep fighting! I'm always by your side, but I'm rooting for you.
You worked so hard and did such a great job as a special MC on Music Core, so it is amazing that you made it to the regular spot. Congratulations, and I look forward to your future endeavors.
I'm Lee Sang-hyeok, please take good care of me. Let's do our best together. Fighting!
❤️❤️

The birthday post for Seongho that Liu uploaded on Weverse!

You look pretty even while sleeping, and the letter is so touching ಥ_ಥ Human F is moved