Regarding of My Married Life with a Childhood Friend Whom I Thought was a Boy going Way Too Smoothly. is a Manga/Manhwa/Manhua in english language, ROMANCE series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Shuichi, a high school student, ended up marrying his childhood friend whom he thought was a boy. At their reunion after 10 years, his childhood friend Yuika had transformed into a beautiful girl, which initially made Shuichi quite nervous. However, as time passed, he gradually grew accustomed to the sense of closeness as best friends— and thus, their love story as an ideal couple with a charming touch of innocence begins!