u/blek_blek

The current Chiikawa movie demonstrates how desires corrupt and bring forth conflicts between parties, despite the desires are not driven by foul intentions and the end goal is supposedly meant no harm to anyone, the means to achieve the goal would inevitably lead to harm. Such theme is eternally sung since ancient times, Greek tragedies have encompassed these conflicts in plays like The Odessey. The sirens are also victims; they would die if they failed their missions to seduce. In Chiikawa's movie, the siren sings and the 3 mermaids are there to harmonise the song, the so-called triad chord (like E-G-B or C-E-G chords), losing one would disrupt the harmony and connection in the music, the magic is now lost forever. It pains the siren every time it sings as it reminds that the music is now less than perfect and will never be perfect again, because a longtime friend died, eaten by one of the villagers. It becomes an eternal torment to the siren and mermaids, it is a pain so deep that the siren deserves revenge in the darkest manner. [it is much much deeper than just music, there are some histories behind it too, that their species likely suffer the hunting from others when there is an encyclopedia that records the immortality granted from eating the mermaid. Also the fact that the Siren marinates and cures the villagers in sauces before eating them is actually darker, the villagers feed the Siren so much (by sacrificing some and luring other innocent outsiders) that the Siren now learn the way to cook the villagers.]

Such is also the worldview that persist in East Asian cultures. They have seen history as a cycle of conflicts and resolutions, ultimately everything is meaningless, beauty is short, elegance is temporary and poignance seems to be the eternal theme. Chiikawa as a species would also be transformed under circumstances just as nature destined it to be.

Now allegedly the next developing theme is can you accept when your friend lied and was a monster to begin with? Momonga's soul was swap with Dekatsuyo's. Is there peace between the chimeras, monsters and Chiikawas? The answer has been given by the Siren, peace is always temporary as they have fundamentally different worldview and roles in the food chain.