I was about to make the point connecting this story back to chapter 1 as it took me off-guard.
Considering the order of events
(tragedies) in the introductory page I assume the MC's other family accidentally fell victim to his mother's curses though it's a rather dark irony that the fire she presumably invoked which decimated the village also acted a signal to help save the MC from dying in the well.
Thanks a lot for picking up this orphaned Koike Nokuto work BTW, alongside
Tonari no Jii-san and
Yuuan no Kanata.
Any interest in the future in further rescuing some of the author's other works like
Kuromachi and
Mushroom?