Gegege no Nyobo

Both give an insight into the life of manga artists and editors, even though Gegege no Nyobo specifically focuses on the life of Mizuki Shigeru (whose name is mentioned two times in the last episode of Juhan Shuttai) and his wife.

Both dramas are based on an autobiography of a real-life figure in Japan.
Both are also set in Japan from the past era.
There is also a little bit of story about the effect of WW in Japan.

The difference between the two:
Tenno is about a guy who became the emperor cook, whereas Gegege is about the life of Gegege no Kitaro mangaka from his wife point of view.
Gegege has a longer eps (Asadora) whereas Tenno is short like a typical Japanese drama.

Both titles are asadoras that focus on a married couple, instead of just the heroine. The heroines’ husbands in both series are well known real people and are portrayed as kinda strange. Most importantly, both have Matsushita Nao and Matsuzaka Keiko in them.

Both based on a true story and in the Showa era. these two Asadoras tell the story of manga artists and their struggles in life and the heroine who supports the hero as the manga artist.