19th Century writer Hugh Kingsmill once said “friends are God’s apology for relations”. In a modern era where certain factions – whether generational, political or moral – have emerged in the family unit, the concept of friendship has proved an important element to accentuate.

This is not to dismiss the persevering importance of family, but we can all recall times when it was our friends that were there for us. In Sunny, we see the power not just of friendship, but how its clout can be maintained even as contact is lost and then recommenced.

It is also about simply losing friends. How we can create bonds that feel as if they will never be broken, only to be followed by decades of radio silence.

Na-mi (Yoo Ho-jeong) is a wealthy housewife and mother to a surly and indifferent teen daughter. Her picture perfect life in a luxury home glosses over a largely unfulfilled existence. She goes to visit her mother in hospital and sees her old school friend Chun-hwa, who has terminal cancer.

She starts to reminisce about her school days, where she joined a new school as a country girl and was taken under Chun-hwa’s wing. Na-mi joins the group of girls which includes the cosmetics-obsessed Geum-ok, the sweary Jin-hee, bright aspiring writer Geum-ok, the Miss Korea wannabe Bok-hee, and the quiet and beautiful Su-ji who seems to have taken an instant dislike to Na-mi.

With Na-mi accepted as the group's seventh member, they are embroiled in battles with another septet of schoolgirls. After asking a radio host for suggestions, the group decides to call themselves ‘Sunny’, complete with the too-catchy Boney M. song of the same name as their theme tune.

With Chun-hwa seemingly fighting a losing battle against cancer, she requests that Na-mi assembles the gang together one last time. We then switch between her current task and various flashbacks to their school days, where we witness the girls pulling together through various conflicts and battles.

In a film which is like a ray of sunshine, uplifting but sometimes bittersweet, the direction of Kang Hyeong-cheol becomes so important. He manages to inject so much energy to the shots, often allowing the camera to dance and turns within the group of girls.

There are some slightly muddled narrative devices and story passages. This is an emotional piece of filmmaking with loose pages of drama and story-telling. Sometimes the emotional impact of a film is so vast, this does not matter in the slightest though. That is surely the case with Sunny.

Sunny is chiefly a love letter to friendship. Its power to support us, to hurt us and to survive time and distance. It will make you want to reminisce about old friendships and perhaps even contact those friends. To produce that level of influence suggests a film of true cinematic power.