While certainly no masterpiece of martial arts filmmaking, Ninja Assassin proves surprisingly enjoyable for the oft-ignored teenager inside all of us. Korean pop sensation Rain is more than adequate as Raizo, the killing machine of the title, raised by the mysterious Ozunu clan, who for thousands of years have trained orphans to become weapons of mass destruction.

The massacre of a yakuza clan attracts the attention of Mika (Naomie Harris), a Europol forensic researcher based in Berlin, who connects the bloodbath and the movement of strange quantities of money to a string of high-profile assassinations dating back hundreds of years. Her obsession with the secret ninja organisation doesn’t play at all well with her boss, Maslow (Ben Miles), until Raizo saves Mika from one of his own deadly Ozunu brothers. Raizo, it seems has been disavowed by the clan, who now wants both him and Mika dead.

Director James McTeigue (V For Vendetta) was certainly paying attention all those years he spent working with the Wachowskis on The Matrix trilogy. Whatever reservations viewers may hold about the lack of nuance in Ninja Assassin’s plot or characterisation, visually the film is a knockout. Each of the numerous fight sequences is staged in a deliberate yet unique setting, whether surrounded by fire, drenched in rain or leaping across rooftops. Each one comes alive on screen, rather than blending together anonymously as can happen only too easily in action films.

Ninja Assassin is surprisingly violent, with heads, arms and other assorted appendages being readily hacked off, sliced and diced, accompanied by copious amounts of CG-enhanced arterial spray. There is also an arsenal of exotic weaponry showcased throughout, including swords, throwing stars and Raizo’s own weapon-of-choice, the kusarigama (a long chain with a blade at one end), that will make young boys’ eyes and imaginations sparkle.

But it’s not all boys-own fun. Softly spoken and heavily accented he may be, Rain proves an eye-catching screen presence, not least when he finds an excuse to take off his shirt, which is often. Rain is ripped beyond belief and McTeigue ensures plenty of screen time is devoted to his leading man’s toned torso, as he fights, trains, showers or simply stands there. But it’s hard to begrudge the filmmakers for milking their surest prospect, even this shamelessly.

By no means a good film, Ninja Assassin is at least frequently a fun one, with enough moments of high octane comic book violence and gratuitous muscle flexing to keep its target demographic entertained until the credits roll.