Now
IF Toshio wouldn't keep the fact Iwao was already dealt with by Natsuno from Motoko, for some reason, the both places would be untouched... this wasn't explained at all why he did that.
As gruesome it may seem, Sunako is at least +300 years old, she has killed at least thousands people herself and even ordered or deceived innocent people to commit murderer against their will.
Doubtful what Tomio told Sunako came through, although at first told Seishin the truth but...
Sunako and all Shiki bear sins, they all look and act human, it's just their food source is different.
It's like being a vegan is allowing a person to commit murder...
I'm pretty surethey're walking in human world, not some imaginary dark wasteland.
This reasoning Seishin is feeding Sunako, will make her even more detached from reality and freely commit even worse atrocities as "we're not driven by human morality, so let's make genocide".
Oh boo hoo, sure he was the only son, Seishin mother tried hard to have a child, but he could always leave and never return, they could be heartbroken but if it bothered him so much to take his own life away as they very much knew, they wouldn't stop him. This is so much stupid.
In the end, there was no happy ending, whole lot of innocent people died and those who survived left with tremendous amount of mental trauma from loosing their families to the fangs of Shiki.
The main culprit is left out alive with her minion having twisted sense of morality, which will most likely lead to another slaughter of innocent people and damaging their families for life.
Overall a "meh" story, plenty of times characters made most dumbest decisions without common reason, especially Toshio keeping Motoko in the dark about Iwao death and Seishin going to Kirishiki mansion with knowledge of Shiki situation but not informing anyone in the temple that made them all being killed as collaborators of Shiki.
5/10