Fuyuhiko distances himself from others on the island because they show him kindness, which as a yakuza, he isn't accustomed to receiving. He also avoids Peko because she reminds him not only of his little sister, but of the past, in better times. When Peko is being accused he desperately tries to defend her, because he realized he not only needed and wanted her by his side during all this, but because of the remembrance of his sister it brings. When she is found guilty he's upset and he cries because he was afraid of losing someone close to him once again. So during Peko's execution he tries his best to interfere to save and protect he, so,ethimg he had failed to do for his little sister. When she dies and he almost gets killed in the process, he realized that running from his past did nothing for him and resolved to stop running from the past.
