On February 9th,Jaejoong attended Hyde's L’Arc~en~Ciel Concert MMXX in Saitama Super Arena. After the concert, it was said that Gackt prepared a surprise birthday party for Hyde, Jaejoong and Hiro (member of 'MY FIRST STORY' and the brother of Taka, the vocalist of One Ok Rock). The 3 of them share close birthday dates by the end of January.

It's a well known fact among fans of both sides that Jaejoong has been a long time big fanboy of Hyde since his teenage days, and that's how he was even inspired to start Rock as a solo artist, Jaejoong got to meet Hyde years ago but he was finally able to get real close to his favorite Rock Star after he started promoting in Japan in 2018, Fans were delighted to see many of their interactions since then.

At Music Station: 

At Hyde's Halloween party 2018:

Jaejoong got to meet the legendary X-JAPAN's Yoshiki and more at Hyde's Halloween party:  

Daigo, Yoshiki, Jaejoong and Hyde on the same stage:

More interactions with J-Rock legends:
toshI of X- JAPAN talked about his experience meeting JaeJoong during Fuji TV's FNS End Year Music Fest 2018 on his official Blog: 

"... In between, I had a long talk with JaeJoong-san.
Sure thing he's an Ikemen -(extremely handsome)-,
His singing is wonderful too,
His personality is also very wonderful!
I want to sing together with him someday
I asked him this favor."

Jaejoong with J-Rock Legend Sugizo, member of  Luna Sea and X-JAPAN at the backstage of TV Asahi's "M️USIC STATION ULTRA SUPER LIVE 2019" 

Jaejoong's caption: "Woah 🙀🙀🙀🙀🙀🙀🙀🙀🙀🙀
I'm really trembling!
I felt really nervous for the first time since I met Hyde, YOSHIKI and Toshi! 🤤"

Gackt invited Jaejoong to his concert:

Translation: "Gackt-san, congratulations for your 20th anniversary
Sincerely thank you so much for inviting me to a wonderful LIVE ^ ^
I got the energy to work hard even in my 40s and 50s!
I'll do my best even more ^ ^"

DAIGO, GLAY's TAKURO, Yutaka Kyan, SYUUSUKE SAITO and more having another birthday celebration for HYDE with Jaejoong's presence:

Seems like Jaejoong is living his fanboy dream and fans are happy for him.