The trailer for Five Hearts Under One Roof Season 2 has appeared on the Steam demo page. Although the text and audio is in Korean, it offers some interesting snippets. Go to the Steam page or watch the trailer below.
First thing to notice is that it seems like all the dialogue is live recorded. There are only a few lines of dialogue here but it definitely does not seem like ADR.
The newcomer Yoo-jung Yang appears to have a few random jobs, at the start it seems like she’s working in the hospital as a cleaner. Later you see her in a giant mascot suit.
Another new cast member, Yu-na Jeong (below), appears in the Hospital and might be the one responsible for injuring Yuman, that could be why she feels responsible for him. She appears to have a bodyguard/assistant shadowing her.

As expected, the third newcomer, Gyu-ri Bang, is the nurse that looks after Yuman and signs his cast.
Min-jung Park looks to be in disguise as she comes to visit Yuman in the hospital.
Mal-sook Go appears to be riding a skateboard.
Maid uniforms are also back, which seems to be a favorite of Storytaco having now been featured in both Five Hearts Under One Roof and Don’t Fool Me, Beauties.

The demo is due out sometime this month and will include the first chapter of the game. A demo for Beauties and the Stranded is also due this month. Both games have had many recent Steam updates and may be going through an approval process now.
Edit: Trailer replaced with English version.