Both shows revolve around a group of close friends who are in the workforce for a number of years. While BTIMFL has more romance, both dramas show workplace struggles and explores concerns about settling down.

There's also a quote from BTIMFL that always comes to my mind while watching ROTP: "Seoul is too cold."

Seemingly-innocent games like children's tag runs and escape rooms but people literally die :( Participants in both shows didn't have a choice in joining (or were tricked to join) but now they have to win for survival

If you liked the chemistry of Shi Guang and Yu Liang in Hikaru no Go, you'll definitely like The Untamed.

Shi Guang is definitely a modern version of TU Wei Wuxian. Both are mischievous, friendly, geniuses, snarky, funny, and loyal. Yu Liang is also very much the same as TU Lan Wangji as they are both serious, quiet, and prodigies. Even the dynamics of their relationships are similar, being bickering frenemies-to-"bestfriends".

Both HNG and TU are not focused on romance and have strong character development plots.

Oh and Ji Li (HNG Gu Yu) is also in The Untamed as one of the main supporting characters.