KHR book 1: the independant life of our beloved sky

Tsuna got his first kill at age 18, some of his guardians left and abandoned him except for chrome. Then he gave up and gave it to a new Sky. 2.5 years later the vongola are happy with their new sky except for chrome, I-pin futa, bianchi, prefect cloud little sister. But what about our abandoned sky?( I know my new summary suck but it's the only thing that I can come up with)