The manga uploaded here is "Yokohama Kaidashi Kikou" - http://www.mangago.me/read-manga/yokohama_kaidashi_kikou/
The real "Yokohama Monogatari" by Yamato Waki:
https://www.mangahere.cc/manga/yokohama_monogatari/
http://fanfox.net/manga/yokohama_monogatari/
Note: 3 Volumes (Hiatus)
Otoko Mekake by Mizukami Shin https://www.mangaupdates.com/series.html?id=83610
❖ƸӜƷ❖ Ch 1-3 Male Mistress - Military // Historical // Showa Era // Shota
After Hayato's father, an army officer, died, he remains alone with his sick mother and with no money. He drops out of school but can't find any job: the only way out for Hayato, who is only 15, seems to be that of becoming the mistress of a danna, who was a friend of his father and paid the medicine for the mother...
Ohana To Chocolate