Recommendations

Ice World is the Japanese original series.
Siren's Kiss was said to be an adaptation of the Japanese drama.
Both dramas have a mysterious female lead.

A tragic accident kills 48 people, leaving the survivors and those connected to the event forever changed. Lee Gang Du, once a hopeful soccer player, now struggles with physical and emotional pain while caring for his sister and paying off a debt. Ha Mun Su, a survivor of the accident, is haunted by nightmares. She lives above her mother’s bathhouse and creates architectural models for safety in major building projects. Years later, a construction project at the accident site stirs painful memories for all involved. As they cross paths, they help each other heal and find new hope for the future.

Same FLs plot where their soul switch to another body.
Same MLs background where their working for the kingdom as investigative field.
Also, same troupe of couple where they are lovers from their past lives before the soul switch.

FL in spring fever acted as the first love of ML in Find Me in Your Memory.
The same actor Joo Seok Tae is the psycho villain in both dramas.
Spring fever is more light hearted rom-com and Find me in your memory is more melo.
Both Romance and lead characters' chemisrty are good.

small details that I find between the drama, which are quite similar
FL makes major career changes (continuing with education & job changes)
calm ML that charms (in one way or another) the FL after a break-up, energy boost
use of tulips and clothing pieces (oversized trench coats & more)
parent health concerns (cancer and mobility issues)
strong family dynamic on the FL side, weak or distant ML side
FL nearly married at an early stage of the show
ML has a side hobby or job that doesn't suit others in their main profession
ML comes from a wealthy background, and FL is relatively normal (not poor)
FL makes the ML life a little more chaotic or lively
Integrated with each other's work lives
FL initates first kiss drunkenly

There's definitely some diffrences but I couldn't help notice the similarities just 13 episodes in

If you are looking for blonde delinquent with a softie inner self, these dramas have both. Being adaptations from a manga, they have anime-like kind of acting which is eccentric to see IRL but the actors in both pulled it off. I already knew it since the MLs in From Today, It's My Turn!! have an established name in the industry but Kateikyoshi no Kishi Knight desu has relatively new faces but if you are doubting, you should give it a try. The story is simple but so promising.

Both are about someone from South Korea in Japan where they meet and fall in love with someone there.

Both are sweet romances between people of different cultures.
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Both MLs blame FL for the death of his family member, keeping her in his house and taking revenge upon her while being caught in a love/hate relationship with her.

Both are mini dramas in which the leads are in a love/hate relationship, with FL blaming the ML for her father's death and the ML a complex, morally grey character with a past connection to the FL.

Both MLs are unassuming guys who suddenly gain a superpower and find themselves fighting with bad guys and surrounded by a group of romantic prospects.

Both MLs are unassuming guys who suddenly gain a superpower and find themselves fighting with bad guys and surrounded by a group of romantic prospects.

Both are Japanese BLs about best friends, one of whom is secretly in love with the other. Both dramas have a similar vibe.

Parallel universes bring together a monarch and a detective in a fantasy romance, similar to crossing real and alternate realities for love.

A girl realizes she's in a webtoon and alters her romantic fate, echoing the blend of creative industry escapism and virtual world dynamics.