Oak boards cover the chamfered entrance to this hair and beauty salon in Osaka, renovated by Okuwada Architects Office to look like a cave (+ slideshow).

The Mook salon is located along one of the narrow streets in the Japanese city's Nakazakicho neighbourhood, which is populated with terraced houses known as nagaya and low-rise apartment blocks.

Facing onto a gently curving alleyway, the salon has been running for 12 years and was in need of a makeover after rainwater began creeping in.

Tasked with renovating the 82.7-square-metre space, local architect Takeshi Okuwada lined the walls and ceiling inside with untreated oak planks.

The wooden boards were also added to the surfaces angled inward around the recessed glazed frontage. The intention was that "the entrance facade would seem to be blend in with the street, and the scenery of the diverse town."

Okuwada described the spaces around the entrance as caves, which are separated by a column that divides a larger window from the double doors.

Inside, a small waiting area is positioned beside the reception counter, which is finished with a mortar screed.

Along the other side, a series of reflective boxes with different dimensions provide mirrors for clients as well as storage for utensils and products in each side. Each box is accompanied by a leather-upholstered chair.

"The feel of the materials corresponds to the purpose and use of the space," said Okuwada, who has also designed a hillside house that faces the Pacific Ocean. "They harmonise the light and time of the space, and give people a moment to feel it."

A pair of concrete screens obscures the sinks for washing hair, which are tucked behind the reception desk.

On the other side is a small WC and an extra room that can be used for treatments.

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Hair and beauty products are displayed on shelves at the back of the main salon area, which is lit by exposed light bulbs hung on cords of different lengths from the ceiling.

The polished concrete floor extends out beyond the floor to ceiling windows facing the street, creating steps down to the road.

Japan is home to a variety of weird and wonderful hair salons, including one with mirrors hung from cords attached to the ceiling and another divided by diamond-shaped partitions. There's even a forest-like beauty parlour where birch trees are wedged between the floor and ceiling.

Photography is by Keishiro Yamada.