Recommendations

-FL is transported into a novel
-FL is considered a side character
-FL gets tangled with the original ML while rooting for the original heroine of the story
-ML also have cold and ruthless/possessive traits

There is a cold character and a very energetic character in both series. One of the main characters tries to make the other's life happier/easier in his own way. Later, the other main character starts to soften and become attached to him. Both characters have past relationships. They love going each others room/condo.

In both dramas, the leads meet friends in their own unique ways and embark on a journey together, facing all obstacles as a team and overcoming them through teamwork.

Complex female lead, well-written gray male lead, and a strong cast of richly developed side characters.

Both dramas are set in the Ming Dynasty and feature strong, independent female leads at the forefront.

Both dramas are set in the Ming Dynasty and feature strong, independent female leads at the forefront. Also, both of them are written by the same author.

Both dramas are set in the Ming Dynasty and feature strong, independent female leads at the forefront.

+ both dramas contain strong male and female leads
+ both dramas have supernatural elements
+ both dramas cover heart wrenching painful pasts and journey

Both have a strong mafia/gangsta element that keep the story going. The romance between the main character is chef's kiss in both series and if you love mafia groups "political" intrigues you will love both series

In both dramas the main characters do a job related to people that have recently passed away that consits of resolving mysterious deaths using technology as a way to bring closure to the case. Both use a computer program/software and work for an organization/company as the main theme of the show. The moral question arises as to whether it is right or not to look into people's personal information and secrets. They share two male protagonists plus a female support character. The two of them share the tsundere/cold vs innocent/kind trope dynamic and a close platonic relationship is formed between them.

Definitely if you liked Shopping King Louis / Shopaholic Louis you will like Attic Cat. And the other way around.
They are not the same in everything but they share a lot.
A rich man (without a house to live, for reasons) meets by chance a poor but clever and hardworking girl. They start living together on a rooftop. They need to be frugal but the MLs in both shows are kind of shopaholics and capricious. Sometimes they act like spoiled children and sometimes like lovely puppies
FL and ML soon become friends, and they are so close that they can't be far from each other even a day. They need to be together like the air to breath. In both dramas the FLs start working for a firm and they get close with their bosses, making the MLs jealous.

In Shopping King Louis there is a love triangle, while Attic Cat is more a love square.

Older female lead, younger male lead. Sweet romance. Relationship growth, life… charming male leads.

Older female lead, younger male lead. Pianist lead. Music . Love, romance… obstacle, challenge, sweet, lofe, relationship,

The Paradise of Thorns (2024), where the male protagonist is emotionally and financially manipulated by his lover’s family, and Moonlight Chicken (2023), where themes of inequality, emotional betrayal, and the imbalance of power in romantic relationships are also explored — especially how one partner’s background or circumstances leave them vulnerable.
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-Male leads suffer injustice after having his property/money taken away by his partner’s parents.
- Fighting poverty and trying to make a living.
- Death and grief of loved ones.
- Marriage equality issues.

Similar setting where the female main character gets transported to ancient time, ends up as a slave, and has to buy her own freedom using inventions and ideas from the 21st century.