I just watched "The beauty inside" and there was a part where the hero cried because the heroine left him, and I got curious if there are other dramas that had a similar scene. Hope you can provide me some recs. Thanks! :D

These are the ones which come to mind; all of them having at least one scene when the ML cries because of something to do with the FL (either he left, she did or something happened). I'll add the reason why he gets sad as I remember under the spoiler tag (in case you'll like to know).

  • Another Miss Oh | ML cries when he leaves the FL because he's the reason her life is in shambles. FL is pretty sad as well.
  • Because This is My First Life | ML is sad when FL leaves him for a while.
  • Black | ML is sad when a serial killer claims to have killed the FL and he can't find her.
  • Come and Hug Me | ML cries when he thinks about all the pain his father caused the FL.
  • Cunning Single Lady | ML cries when he discovers the real reason of why the FL (his ex-wife) asked for a divorced.
  • Devilish Joy | ML cries when he remembers the FL and realizes that there's no cure for his disease. 
  • Feel Good To Die | ML cries when something happens to the FL but he's unable to go back in time to fix it. He also cries when he realizes he loves the FL but believes she doesn't love him back.
  •  Gu Family Book | ML cries when something happens to the FL.
  • The Greatest Love | ML cries when he thinks he can't win the FL back.

https://mydramalist.com/27225-tra-barb-see-chompoo I've seen some scenes from all the episodes, still have to watch it full, and I swear I've never seen a guy cry as much as him because of her and the family circumstances. 

If you don't mind fantasy historical - 

https://mydramalist.com/23281-heavy-sweetness-ash-like-frost 

https://mydramalist.com/16547-eternal-love 

I see you have Addicted Heroin in your Plan to watch so you don't mind BL, so check out https://mydramalist.com/22646-history-obsessed 

  • Werewolf Boy 
  • Fated to Love You 
  • It's Okay that's Love 
  • That Winter the Wind Blows 
  • Robber
  • Fantastic 
  • Gu Family Book 
  • All in 
  • Thirty but 17 
  • King in Love 
  • Scarlet Heart ryeo
  • Devilish Joy 
  • Please Come Back Mister 
  • Hwayugi 
  • Into the world Again 
  •  are you human too 
  • I am not a robot 
  • My Strange Hero 
  • About Time 
  • Millionaires First Love 
  • Shine or Go Crazy 
  • Clean with a Passion 

Thanks for your recs everyone. :)