A tiny Japanese baby who weighed just 258g (9oz) when he was born five months ago is going home from hospital.

Ryusuke Sekino was shown on Japanese TV sitting in his mother’s arms, looking sombrely around at media cameras.

His mother, Toshiko Sekino, told reporters she was worried and cried a lot at first because he was so fragile and had transparent skin.

She said she can now breastfeed Ryusuke and is looking forward to taking him home on Saturday and giving him a bath.

Ryusuke Sekino with his mother Toshiko Sekino and father Kohei Sekino
Ryusuke Sekino with his mother Toshiko Sekino and father Kohei Sekino (Kyodo News/AP)

The University of Iowa keeps a Tiniest Babies Registry, which shows the previous smallest surviving boy weighed 268g (9.5oz) when he was born last year in Japan.

A German girl born in 2015 weighed 252g (8.9oz).

“There have been difficulties in the treatment because, immediately after his birth, his blood vessels were too thin to administer intravenous drips,” said Dr Takehiko Hiroma of Nagano Children’s Hospital.

He said Ryusuke is healthy now and weighs 3.37kgs (7.4lb), Kyodo reported.

Japanese media said he measured 22cm (8.7in) in length when he was born.

“I can really feel his weight now. He used to be so light,” his mother said on Fuji TV news.