The Time We Were Not in Love

Time is a woman's enemy. On her 30th birthday, Cheng You Qing received an e-mail from Li Da Ren, her male best friend of 14 years, about the symptoms of premature aging. Unable to bear the fact that, as a man, Li Da Ren is likened to a fine wine that gets better with age and that as a woman, she is likened to a grape that will dry up like a raisin over time, she makes a bet with him to see who will marry first before they turn 35.

As she scouts for a potential husband, she finds that despite whoever she meets, there is always one person whom she can be totally at ease with and who is willing to put up with her independent, ill-tempered and stubborn personality - her best friend, Li Da Ren.

The only problem is that the both of them had already sworn to each other that they would never fall in love with each other.

Choi Won is "the perfect guy" - good-looking, tall and fit with an amicable personality. Although he is very popular with women, he can't have a proper relationship because of his friend, Oh Ha Na. A romantic comedy about a man and a woman who have been best friends for 20 years (7000 days). They turn 34 and make a pact to be married before 35, and race each other to the altar while “helping” weed out potential suitors. They find that they're constantly dissatisfied with each other’s boyfriends and girlfriends, because they've really been in love all this time.

Best friends turned into lovers. But there is a rough process before that two become a couple and admit that they loved each others

Romantic comedy about best friends for almost 20 years. They make a pact if they reach 35 years old and do not have any relationship, they will marry each other.

K Drama with a similar story of how MML was in love with the FML from high school but never confessed and how both MML and FML were in relationships with others but never worked out for them .

Friends to lover. The time we were not in love Korean, Honno Switch Japanese.
Also have a little similar vibe

The story of childhood friends who are in love with eachother, and of course the third parties that they meet along the way (love triangles! or squares?)
Both have a similar air, where they are not that extremely dramatic or serious but are light hearted in a sense.

pretty much the same story line, best friends who come to look at the all years that they have been together as friends and try to understand their real feelings and the line between friendship and love.

Shibasaki Himari (27) is a cheerful and straightforward woman who works at a PR company. Despite her bright outward appearance, she has a strong sex drive, and a history of breakups caused by sexual incompatibility has left her with lingering emotional scars.

One day, as more and more of her friends get married, Himari begins to feel anxious about her own future. As usual, she vents her frustrations over drinks to H?j? Kazumi, her best friend since college and now also her coworker. Unlike Himari, Kazumi has shown no interest in finding a long-term partner and seems completely unconcerned about it. However, when Himari says she wants to meet someone she is truly compatible with, Kazumi suddenly suggests, “Why don’t you try it with me?”

Surprised by this unexpected proposal from someone who had always seemed to keep a certain distance between them, Himari is conflicted. Yet despite knowing they are best friends, the two end up crossing that line. As a result, their relationship, once built on complete honesty and friendship, begins to change.

They could always be honest with each other as friends. They thought friendship was enough. But burdened by their respective pasts, neither had been able to take the next step. Now, as they move beyond the boundaries of friendship, they find themselves caught between friendship and love in this sweet yet risky romance.

The story lines are definitely different, but both of the main roles are friends since they were young. They know each other's habit and have an undescribed feeling for each other not knowing it was love as they growing up together.

Lin Zhen Xin is an ordinary office worker who gets ridiculed by her subordinates. Dejected, she listens to a cassette recording of an old Andy Lau song. This brings her back to her high school days, where she was an ordinary high school girl. She has a crush on Ouyang Fei Fan, the school's most popular male student.

One day, Zhen Xin receives a chain letter, warning her of impending doom if she does not pass the message on. Naively, she passes it on to Hsu Tai Yu, the school's notorious gangster boss, her maths teacher, and Tao Min Min, the school's most popular girl. While Tai Yu was reading the letter, he gets injured in a car accident. After weeding out the letter's sender, the angry Tai Yu makes Zhen Xin his 'friend' and forces her to run errands for him in exchange for leaving Fei Fan alone, thus making her his errand-girl.

While on vacation in Hokkaido, Natsuki happens to meet Soichirou, a photographer. Unbelievably, she runs into him two more times completely by coincidence, and out of this, a great friendship is formed. He turns out to be the younger brother of one of her best friends, and they all end up living under the same roof. Three women, all unmarried, and all nearing age 30, plus 25-year-old Soichirou. Can a man and a woman truly be friends without ever falling in love? How large is the line between friendship and love, or does it even exist at all?

Both are sweet and steady paced dramas. Also, the male lead loves the female lead and doesn't waver through both series. Only difference is that in Boss&Me they get together in the beginning of the series and TWWNIL it takes them longer.

Saimori Miyo was the unfortunate child of a loveless, arranged marriage. After her mother died, her father brought in his lover and her own daughter, Kaya. From then on, Miyo's life was reduced to that of a mere servant. Even worse, while Kaya inherited the family's psychic abilities, Miyo had none—she was truly the daughter with no merit. After years of being treated like dirt, Miyo has learned to keep her head down, hide her pain, and obey every order. So, it comes as no surprise that she is arranged to be married to Kudo Kiyoka, a military captain rumored to be so cruel that he has driven away every one of his potential wives so far. From a painful upbringing to a painful marriage, that's the future that awaits Miyo—or so she thinks. Contrary to her expectations, her new husband is actually kind-hearted. What really awaits Miyo is a blissful, everlasting marriage full of happiness!

Both deal about friends who realize they feel more than friendship for the other person. Both deal about the nearly same story, so if you like one of them you are bound to like the other as well