SS501 singer Heo Young Saeng left a final message to fans on his Twitter account before he reported for duty at South Korea's Nonstop Training Center on Thursday.

Heo is the second of the five members of the K-pop boy band to enlist. SS501 singer Kim Kyu Jong began serving in the Army in July of 2012.

"I'm finally going," the 28-year-old vocalist wrote to his 213,000 Twitter followers.

"The day that Kyu Jong left just feels like yesterday. But, I'm suffering from a cold. I will always look after my health next year. Stay healthy, and I wish you the best luck."

Heo told his fans there would be no final photo before his enlistment, on account of him being uncomfortable with his new army regulation hairdo.

"There is no last photo, because I feel too awkward with my [new] hair," the SS501 singer wrote.

Heo will serve for the next 21 months as a civil police officer, according to the publication STAR N News. Kyu is reportedly completing a 24-month non-active enlistment as a public service worker.

All eligible South Korean males between the ages of 18 and 35 must enroll for roughly two years of army service. The exact length of their mandatory enrollment depends on which branch of the military that they serve in.

In a final phone interview on his way to the enlistment center, Heo told eNEWS that while he will serve faithfully, he is also looking ahead to his life after the army.

"Since it's a call from the country, I will be devoted to my time there," he said.

"More than anything, when I'm discharged, I'll be 30. I think it will be a time to look back on everything I've done in my life so far."

"I still have a lot of think about for my future," he added.

"I believe this will be a time to grow and mature. Please be waiting for me when I return as a stronger man."

On Saturday, Heo, who released his own album "Let It Go" in 2011, had the bittersweet experience of his last concert before he entered the army also being his first-ever solo show.

The singer's SS501 bandmates were also on-hand for what was billed as the 2013 Heo Young Saeng Seoul Concert 0513 My Story.

SS501 reunited onstage as part of Heo's farewell to fans.

"My hearts thinking that I won't be able to see you for a really long time, but there's nothing really that we can do, right?" Heo said to the crowd.