On February 7, various online community boards were flooded with photos of the Super Junior member attending the former IOI member's graduation ceremony at Gyeonggi Girls' High School.  It seems Heechul kept his promise, demonstrating their close friendship.

SEE ALSO: Former Lovelyz member Lee Mi Joo and soccer player Song Bum Geun announce breakup

As for Kim So Hye, the idol star took the time to greet fellow classmates and teachers one last time at the special event.

Upon witnessing Heechul's sudden appearance, Kim So Hye couldn't hold back her surprise as she beamed brightly.  Heechul also handed her a gift as the two posed happily for the camera, with flower bouquets in hand.

Previously, Heechul and Kim So Hye met on the set of SBS variety program 'Game Show' where they built a solid brother-sister bond.

Kim So Hye had expressed, "I would like for him to come to my graduation ceremony."

How sweet!