Manga by author Takao Shigeru - Status ongoing

From Aerandria Scans: It's the 1920s and Mariko, age 16, is married to a man 30 years her senior. She is honestly happy to be his wife and really excited to board the Orient express in Turkey on their honeymoon trip. But her life takes a rapid turn when her husband is discovered dead after the first night on board... And that's only the start of Mariko's great adventure.

[From Ivyscan]:Feeling rebellious toward his overprotective mother, Soma Mitsuya, a first-year high school student, only cares about his violin and his hospitalized grandfather. On the night his grandfather's condition suddenly worsens, an earthquake hits, sending Mitsuya to 1921 in the Taisho era

7th grader Oshiro Shinobu, the daughter of one of Japan's old family lines, was seperated from her parents due to certian circumstances when she was only 6. Because of this she now lives with one of her distant relatives, Kouda Shougo, who is a teacher at the school she now goes to. Aparently, a childhood friend by the name of Oku Saizou is transferring into Shinobu's class, but wait... This timid and hesitant boy is actually a ninja who serves Shinobu and has come for the sole purpose to protect her...?!

From Operation Boredom:Ichiko Usami is a fifteen-year-old runaway girl. One day, while she's loitering around the riverbed with nowhere to go, a masked boy named Kohaku suddenly appears in front of her! Ichiko faints and Kohaku takes her to the mansion he shares with several others. Even while lost in wonderment at the individualistic residents, Ichiko gradually opens up to them. But why is she somehow frightened by the fallen children shoes?