Currently, the hashtag is trending worldwide on Twitter. You can check some of the sweet tweets for Kihyun below. 

Happy Birthday, Kihyun!

To the guy with endless love, energy, and passion to share in his life with everyone...Happy birthday Kihyun!!!!!!
i wish you only the best today and always!! Let's keep reaching higher and show everyone the true artist you are!! ILYSM~!!!! @OfficialMonstaX #1122KIHYUNDAY pic.twitter.com/DTU2QJXcis

— nettie, KIHYUN DAY!! (@kihyunsnena) November 21, 2018

Thank you for being Monsta X's Kihyun, for being my happiness and most importantly for being born. I love you with all my heart and I want to spend many years hearing your beautiful voice. Stay the way you are & never change.#1122KIHYUNDAY #1122HBDKIHYUN pic.twitter.com/7TOwWLJ5FD

— [hiatus] Sevim (@sevimxmb) November 21, 2018

happy birthday to one of the kindest, strongest, most comforting people i know. you make us so proud, thank you for being so fiercely passionate about life #1122KIHYUNDAY pic.twitter.com/pqmnmWJWM7

— n (@wonhocity) November 21, 2018

Happy Birthday
Love Yoo Most#1122KIHYUNDAY #?? pic.twitter.com/LtV0suo2dF

— NO MILK TODAY (@NOMILKTODAY_) November 21, 2018

happy birthday kihyun! thank you for always sharing your photography with us, your photographs are always so beautiful and i'm so proud of the effort that you put in to this interest. hopefully we'll see more of your hard work through another exhibition soon #1122KIHYUNDAY pic.twitter.com/59C8EHgMA5

— cIoita (@kihuyks) November 21, 2018