Another thread from a poster from Reddit:
"Having finished the manga today, I was quite disappointed nothing was paid attention to Hermit's step mother and the poisoning since the backstory flashes implied she might be innocent and that Hermit would have a story arc devoted to resolving family issues.
Instead what we got was a feeling of unfinished agendas much like Zuko (from Avatar: The Last Airbender) going on a quest for to search for his mom but the series ending before that could happen.
So I am wondering if there has been Gaidens or other material showing this? The flashback really seemed like his step mommy did not do the crime!"