Rarely do adaptions eclipse the original work to the point there's no point in even looking at the original. Yet here is one such case.
In the J-Drama adaption, real life couple Aragaki Yui and Hoshino Gen (they got married after filming this drama) portrayed Mikuri and Hiramasa excellently. The mangaka herself even admitted she thought the script writing and acting for the drama was so good that she changed some characters in the manga to more closely match their counterparts in the drama.
The J-Drama and manga mostly cover the same material except the drama refined some of the writing and plot points to progress more logically. The drama also has a much better ending because it wraps things up before the point where the manga starts to decline in quality.
After the ending point of the drama the manga keeps going and has a two-year time skip followed by one more arc. I was actually very excited for this because the last arc is a pregnancy arc showing Mikuri and Hiramasa's first child but this was the worst arc of the manga. The mangaka admitted she knew nothing about pregnancy and has never had kids and learned everything she wrote about from the internet. It shows. Everything is portrayed in a sanitized, dumbed-down way that doesn't fit with the otherwise realistic portrayal of adult life. Some really difficult parts of pregnancy got dealt with in only a few panels (morning sickness, mood swings) and other issues (restricted movement, heavy feeling in the belly, fatigue, ect.) weren't really shown at all.
Oh, and one more thing that I didn't like about the manga is that side couple Yuri and Kazama break up off screen during the time skip and their story never has a satisfying conclusion. The mangaka wrote in a note that she decided to do this after a friend suggested it would be juicy drama if they broke up and still had feelings for each other. That may be true, but it doesn't make sense for them to break up and it would be better if the characters' actions proceeded logically from the way they've been written -- even if that meant there was less drama.
Well, I think I've written more than enough. Is the manga bad? No. However, since the J-Drama adaption improved upon the story and has phenomenal acting, writing, cinematography, music, ect... just watch the J-Drama instead.