A tense family drama is one of two Japanese films vying for the top prize at this year's Cannes film festival.

CANNES, FRANCE (MAY 18, 2013) (REUTERS) - A film about baby-switching by Japan's Kore-eda Hirokazu that ponders nature versus nurture is among the 20 films vying to take home the Palme d'Or prize from this year's Cannes film festival.

"Soshite Chichi Ni Naru" ("Like Father, Like Son") is one of two Japanese films in contention for the top spot.

Their outwardly picture-perfect family life is shattered one day after the hospital where Keita was born informs them they made a mistake and Keita is not their biological son.

The revelation forces the couple into an agonizing decision -- whether to keep Keita as their own, or make a swap.

Speaking to Reuters TV on Saturday, Masaharu Fukuyama said he was excited to be attending the festival but that playing the part touched a particularly personal nerve.

"I lost my own father in my teens and it made me think about how much he actually did love me. And I also thought about how much love I expected from him so thinking about it in your ordinary life, you don't normally have time to think about these themes but by acting this role it forced me to think about it. In that way, I sort of recalled some of the past I didn't really want to remember so it was a very hard experience for me," he said.

The film finds moments of humour and humanity when Ryota and Midori meet the couple, played by Yoko Maki and Lily Franky, who have brought up their biological son.

Shopkeepers from a different class, they horrify the sensibilities of Ryota, who sees them as bumbling simpletons incapable of rearing his son, but the first impression is eclipsed by recognition of their kindness and obvious love for their children.

Japan has won Cannes' top prize four times, most recently in 1997 with Shohei Imamura's "Unagi" ("The Eel"). Its other offering this year is the stunt-filled police thriller "Wara No Tate" ("Shield of Straw") by Takashi Miike. "Soshite Chichi Ni Naru" is Kore-eda Hirokazu's fourth film to compete at Cannes, his "Kuki Ningyo" ("Air Doll") having been included in the "Un Certain Regard" category for emerging directors in 2009.

The gentle film is a contrast to many over the first four days of competition that have been marked by violence.

Mexican film "Heli" includes a sickening torture sequence, while a man in Chinese film "Tian Zhu Ding" is driven to carry out a bloody rampage after failing to thwart corrupt officials.

A rival family drama, "Le Passe" ("The Past") by Iranian director Asghar Farhadi, also received critical praise after its premiere on Friday.