Both shows are about a girl who finds herself in a foreign country, and how she adapts to new cultures, languages and lifestyle. Both are also fairly moe, especially Kin-iro Mosaic.
The story of a foreign girl learning to live in a foreign land is at the heart of both Ikoku Meiro no Croisee and Kin-iro Mosaic. Both are light, cute stories about friendship, and would probably appeal to the same audience.
As everyone else has said, both shows are comparing japanese culture to different cultures, Ikoku being Paris at the turn of the century and Mosaic being modern-day England. Obviously focusing on two very different cultures and time periods, as well one show is set in Paris, the culture being compared, and the other is for the most part still set in japan.
Neither one is a particularly deep or thoughtful look at cross-culture comparisons, however, choosing to go with a lighter, softer, more moe feel. If you liked one, you'll like the other!
When Daikichi's grandfather dies he leaves behind a young daughter named Rin. However, as most of the family is embarrassed at the idea of a 79-year-old man having a six-year-old child, they can't seem to figure out what to do with her. Disgusted by this behavior, Daikichi decides to take care of her himself, but he's a bachelor, has no idea how to raise a child, and isn't even all that comfortable with kids! Now, Daikichi must do the normal things a parent does such as enroll her in school, buy her clothing and teach her about the life and world around her. But more importantly, he must also help her deal with her father's death and decide whether or not she should try to find her mother. Together, the two begin their unlikely relationship as father and daughter, navigating each of life's bumps along the way.
Both deal with single men having to suddenly take care of a young female child. The interaction works like a father-daughter relationship, and shows the development of having to care for children that may be young and somewhat naive yet mature for their age. Croisee deals with young Japanese girl living in France for the first time during historical times while Usagi Drop takes place in modern Japan. Both have the same slice-of-life feel that focuses more on the endearing and developing interaction between newly-father and child and less on romantic drama.
Both are extremely similar in that a child is left in the care of a childless male protagonist, Usagi Drop is certainly more focused on the relationship between parent and adult whereas Ikoku Meiro no Croisee emphasises differences in culture and a more typical child/adult relationship.
Both of these anime are about a cute innocent little girl coming into the lives of young men who end up taking on a role of looking out for and/or taking care of the little girl. In both, the little girl forces the men to change the way they look at life and grow as people. We also get to see the little girls grow and mature as they experience new things.
In a moment of pure warmth and happiness, it is said that children of the light, known as Tamayura, will appear. Fuu Sawatari is a young girl who loves taking photographs the same way that her beloved father did while he was alive. Having recently moved to the town her family frequently visited when she was younger, Fuu enjoys her life to the fullest alongside her friends Kaoru, Norie and Maon. Whether the gang have a sleepover, chase a furry cat around town, or simply enjoy a delicious lunch, Fuu always has her camera in hand in the hopes of finally capturing the illusive Tamayura on film.
These are both Slice of Life anime that revolve around the everyday experiences of a few characters within a small and tightly knit community.
Slow paced day by day type of slice of life with little happening each episode while keeping a fluffy tone and setting. Both series feature a short statured girl who's personality is meant to appeal to protective people.
The settings couldn't be any more different having a huge time period between them.
Neo Venezia, the pride of planet Aqua, is a quaint city filled with canals and easy-going people. Many companies operate their gondolas on the canals, giving tours to tourists and locals alike, but the most famous of them is the Aria Company. Follow the adventures of Aria's young apprentice, Akari, as she learns the tricks of the trade from her beautiful senior, Alicia. Together with her friends Aika and Alice, apprentices of rival companies, and their seniors Akira and Athena, they train their skills as gondoliers, meeting new people and learning new things about the city each day.
Though these shows have very different premises, they share the same slice of life genre, equally slow pace and heartwarming atmosphere with rather idealistic outlook on life. Both series depict people getting to know new places, meeting various people and learning about their stories of life.
In the early 20th century, Kazuya transfers to a prestigious academy as part of an exchange program between Japan and Saubure, a small European country. But while Kazuya would love to make friends and have a typical school life, the boy is shunned by his ghost story-loving peers who believe that he's a "Black Reaper" to be feared. Things change one day when Kazuya wanders to the top of the library and discovers a lush botanical garden, and a beautiful, small, blonde-haired girl named Victorique who rarely leaves the building and is fascinated by unsolved mysteries. Together, the two develop a budding friendship and take on many chilling and dangerous cases that even the famous local detective Grevil can't solve.
In both series, they involve a character from another country moving into Europe. There, they learn the experiences, problems, and cultures in Mid-Europe. These two series had hinted and showed signs of romance aswell.