By the demented standards of fantasy anime, this is fairly straight; the weirdest thing on show here is probably a unicorn-wolf who scoffs pink frosted doughnuts. And in case you’re having trouble distinguishing the interchangeable faerie folk who populate the cast, this second theatrical outing for the series has (unusually for feature-length anime) a handy explainer at the start: namely that the protagonist is a murdered salaryman reborn as Rimuru (voiced by Miho Okasaki), an amoeba-like blob who rises to become demon lord of the realm of Tempest.

In fact, Rimuru features minimally in this sequel. He and his retinue are invited by the Celestial Emperor to holiday at a luxury island resort; the only thing spoiling their sightseeing, fishing and carousing are the laser-like bursts of “nuclear magic” periodically blasting over their heads. But they are told they are in no danger: the target is the nearby undersea kingdom of Kaien. Rimuru and co resume their vacay – but bodyguard Gobta (Asuna Tomari) realises the group are being trailed by Yura (Saori Onishi), a Kaien priestess who has absconded with an ancestral flute at the centre of a power struggle.

The busy conspiracy knot that follows, involving shady chancellor Djeese (Kōji Yusa) and his attempt to wrest control of the kingdom’s water-dragon protector, is a good lesson in the difference between plot and story. We’re hosed down with the former, but the only resonant bit is the unlikely tryst blooming between Yura’s aquamarine-tressed ninja and Gobta, a kind of top-knotted mini-Shrek sporting a Hawaiian shirt. As Djeese’s goons hunt them down, they get a fun tag-team martial-arts sequence sprinting through the resort’s Venetian streets, like a Bond opening scene.

But as Rimuru’s posse are drawn under the waves to Kaien, this partnership is eclipsed by bland politicking and oceanside smackdowns between the factions. With less daffy humour than previous film Scarlet Bond, the initially so-so animation picks up to a more sublime level by the climax. If the sight of the aforementioned unicorn-wolf surfing a wooden door into the heart of a mega-waterspout suggests emotional poignancy may not be a priority, think again: there is an unexpectedly chilly closure to Yura and Gobta’s romance, apparently transplanted from a Wong Kar-wai movie. Otherwise, this hectic fantasia struggles to plumb deeper depths.