After being killed by the enemy, Tsunayoshi Sawada also known as Vongola Decimo, Byakuran transfer his soul to the parallel world, there he isn't the vongola decimo instead his so called 'perfect brother' know as Yoshiro Sawada.
He acts like an angel in front of many people but when he's inside of their living household he's nothing but a spoiled brat, a greedy bastard to be exact.
Tsuna's mother always protect Tsuna from his brother's wrath.
WARNING ⚠: COLORFUL LANGUAGES and ETC. (Sorry to lazy to write some warnings (。_。) )