Complex sentence: He later unwillingly becomes a part of his sister's plot when she send him to get married with Nagamasa Asai, disguised as a girl and using the name Oichi, later they fell in love with each other.
Split into simpler sentences: He later unwillingly becomes a part of his sister's plot when she send him to get married with Nagamasa Asai, disguised as a girl and using the name Oichi. However, later they fell in love with each other.