At age 33, I am a loser, jobless and virgin, who only has remorse and pity for myself. Called by Anna, my secret crush in my childhood, and her fiance, I come to face the reality. But after I fall from the roof (caught wearing a grade school girl's swimsuit) I find myself to be back in the past. Now I will get my life back.

From: Easy Going Scans
As a result of a strange encounter with a mysterious carcinogenic fetus he found inside a patient’s skull, brain surgeon MINAKATA Jin has slipped back through time. Equipped with modern medical knowledge, he faces various fatal diseases and injuries. Then, he meets the ordinary people of Edo as well as illustrious figures, and his surgical knife carves out a new history and story of life.

Note: Won the Grand Prize at Tezuka Osamu Cultural Prize in 2011.

Released in English by the Artist on his Patreon:
https://www.patreon.com/motokamurakami

Feeling rebellious toward his overprotective and neurotic mother, 16-year-old Souma Mitsuya cares only about his violin and his hospitalized grandfather. On the night his grandfather's condition suddenly worsens, an earthquake hits, and Mitsuya finds himself lost and alone in Japan of the year 1921.

Struggling manga author Satoru Fujinuma is beset by his fear to express himself. However, he has a supernatural talent of "noticing things" that forces him to help people.

Boku dake ga Inai Machi Gaiden