Missing: The Other Side (2020)

Both have 12 episodes, and are great! They have a good pacing movement, and both are just so un-explainable but so great. I really enjoyed Mystic Pop-Up Bar, and Missing: The other side. Even though both have only 12 episodes, I enjoyed the whole experience. As watching, it sometimes get side tracked and off topic, but only for one or two episodes. I hope you guys give both a try, because both are really great!

Both kdramas are mystery/thriller/detective type with a fantasy element to them.
While Tunnel moves between different times, Missing moves between two worlds.

Both titles are kdramas with investigation/thriller/crime element with a fantasy twist. They have similar vibe and touching moments.

both shows have the protagonist solving cases and ultimately having closure for it.... if anything it has the same satisfactory good vibe of a job well done in the end .

Jirisan happens in nature and in Missing it's similar.
These two also have the fantasy/mystery element that really takes a strong part of the story.
There are moments of teamwork for both shows though for different purposes.
In Jirisan, they are looking for people who go missing on the mountain while Missing is sort of a different perspective of searching for those who go missing.