INFINITE's Sungjong sent fans a letter from the military on his birthday.

Sungjong quietly enlisted for his mandatory military service this past July, and he spent his 26th birthday on September 3. He made sure to update fans on Instagram on his birthday with the following letter:

"Hello INSPIRIT.
It's INFINITE's youngest member Sungjong.
On a special day like this, I wanted to give you a quick update on my life. I have been having a fulfilling day today with many kind words from people.
Woollim's CEO, who was the first to wish me a happy birthday, my loving members, our Woollim family, many acquaintances, and precious family members, thank you.
Finally, INSPIRIT, who I miss so much, I'm always longing for you, thinking of you, and missing you. I hope you're always happy.
INSPIRIT, I love you."

INFINITE revealed the below behind-the-scenes clip featuring Sungjong as well. Happy Birthday, Sungjong!