Taeyeon will be singing a song titled "Rescue Me", to be included in episode 3 of the drama, while EXO-CBX's "Cry" will be included in episode 4. According to Japanese media outlets, both songs will only be available through the drama for the time being. 

Taemin also previously sang an OST "What's This Feeling" as the theme song for his drama. 'Final Life' is currently airing in Japan via Amazon Prime. Do you want Taeyeon and EXO-CBX to release these songs as official singles?