Recommendations

Male lead's parent is a serial killer. The male lead is now a cop due to his parent being a serial killer just like the male lead in this Kdrama. The difference is it is the father in come and hug me and in Queen Mantis it is the male lead's mother who is the serial killer.

Letters travel through time through a specific mail box.
In TL, the leads are both in the past and already know eachother. In IM, the leads are split, one in the past one in the future, and they contact eachother through the letters only.

Two souls find each other in the darkest times of their lives, becoming a support, a guiding light, a hope for each other.

Both are BL dramas in which the leads were a M/F couple in the past, and the FL has now reincarnated into a male.

Both dramas are love stories between a couple in which the FL is reincarnated as a male in the present day, and one of the MLs is under a curse which means they have a short time left to live unless they can break it.

Young men seeing and falling in love with a ghost is always a good watch, albeit with some tears mixed in.

Both of these dramas have similarities in the cinematography and the overall angsty vibe, and story vise they are both are time related, where two different timeline can contact each other.

Both have a stand up comedian fl who, after enduring a series of personal setbacks, unexpectedly finds a new path in life by stepping onto the stand-up comedy stage.

These two films revolve around the same concept: individuals from different eras forming a connection through a shared object. In Il Mare, it’s through heartfelt letters; in Ditto, it’s a radio that lets them hear each other’s voices. It’s a stunning and moving story I truly recommend watching it!

Special effects spectacles are similar
Evil vs. good
Enemies to lovers
Arranged marriage
Misunderstandings...i.e. trying to push love interest away to "protect" them
Bittersweet ending, but this one is a little more happier

Story in TTEOTM is a whole lot better and more impressionable imo

Another fusion sageuk with a time-slip premise, except this time it’s a Joseon scholar who suddenly finds himself in modern-day Seoul. What makes it shine isn’t just the clever historical twist but how beautifully it balances romance, humor, and history and the lead chemistry is still considered legendary. Both even use a similar time-travel mechanism tied to text , so if you like the idea of history being bent by love and fate, this one’s a must-watch.

Set in the same era, Rebel: Thief Who Stole the People isn’t a fusion sageuk but a traditional one, but it delivers a layered, powerful take on Yeosangun. It doesn’t redeem him but shows the cracks that turned him into a tyrant. And I think watching RTWSTP will give you a richer lens: you’ll appreciate even more what could change in a time-slip scenario in BOYM once you understand what caused those cracks in the first place.

The story follows Jiang Zhu, a “Jade-Waisted Slave”, who must find a “Jade Gentleman” on the night of the full moon after coming of age, and engage in dual cultivation to absorb his vital yang energy in order to survive the Cold Bone Syndrome. Initially determined to hunt down the Jade-Waisted Slaves, the powerful statesman Shen Miu is unexpectedly affected by a love spell cast by Jiang Zhu, forcing him to protect her against his will.

Jiang Zhu’s passionate and free-spirited nature brings Shen Miu—who is disciplined and suppresses his desires—a vivid experience he has never known before. As they spend time together, they gradually awaken to the meaning of love and ultimately join forces to clear the injustices suffered by the Jade-Waisted Slaves.

Midnight Sun has the better dying musician plot since the disease is named and real. And it's kind of the opposite of Glass Heart in the sense that YUI is primarily a musician this being her only film role - and she's at least as good at acting as the very good actors of Glass Heart at being musicians.

20th century girl is much more emotional but they both are set in 1999 and explore the themes of innocent school love and parting