Kai and Mark are labelmates under SM Entertainment. Kai is a member of EXO, and Mark is from NCT. Mark is seen several times fanboying over EXO and has great respect for the group.
They performed at several SMTown concerts together and were seen nearby each other. Both groups have also had collaboration stages with each other, including a performance of Monster by NCT and EXO at the 2018 KBS Song Festival. It is probable that they had some interactions since they are both idols under the same label, but little of their interactions have been caught on camera, until their debut in SuperM. However, at the SuperM premiere event, Kai admits he hasn't had any deep conversations with the NCT members, and so SuperM was likely the first time Mark and Kai properly interacted.
In late 2019, Kai and Mark debuted as members of SuperM. Dubbed as the "Avengers of K-Pop", the group consists of idols from different SM boygroups, namely EXO, NCT, WayV, and SHINee. At first, Kai and Mark were shy with each other, with Mark even struggling to put his arm over Kai during a photoshoot. However, during preparations for their debut, Mark and Kai grew closer.
Mark and Kai debuted as members of SuperM with the title track Jopping.
- “We were taking photos today and Kai was actually saying... I was actually all over Kai like right now while we were posing for a photo and Kai was like, 'If you think back to the days we filmed this photo...', It was actually hard for me to even put my arm over his shoulder. And we were just kind of recalling that fact that our bond got even closer though they are older seniors. It's very special to get close to people that we always looked up to.”
- — Mark about Kai
- “Mark was so adorable”
- — Kai about meeting Mark
Prior to the debut of SuperM, the ship had little to no popularity, though both Mark and Kai were popular idols under SM Entertainment with huge established fanbases. Kaimark started quick popularity after SuperM's debut, especially after the press conference, where Kai and Mark were shown to be good friends.