Sejima, the female partner of architecture studio SANAA, has been working on the Inujima Art House Project since 2010, when she and art director Yuko Hasegawa opened three galleries and a small pavilion in the island's village.
The two new buildings, entitled A-Art House and C-Art House, will join F-Art House, S-Art House and I-Art House to create a series of spaces that can host coinciding exhibitions.
Clusters of artificial flower petals decorate the acrylic walls of A-Art House, giving a colourful backdrop with shades of pink, orange and yellow to the open-air courtyard that makes up the space.
Instead of a precise circle, the structure has gently fluted walls that bulge outwards, creating an outline reminiscent of a flower shape. A rectangular opening forms an entrance through one of the walls, while silver stools offer a pair of seats for visitors.
C-Art House, the second of the two galleries, occupies a renovated nineteenth-century timber shed near the coastline.
The structure of this building is revealed inside, where ageing wooden trusses are supported by modern timber columns. Timber panels line the walls, while a panoramic screen provides a surface for film screenings.
To tie in with the opening of the new galleries, all five spaces are presenting a combined exhibition where each space is dedicated to the work of a different artist.
Kazuyo Sejima is best-known as one of the two founding partners of SANAA, alongside architect Ryue Nishizawa. The pair were awarded the Pritzker Architecture Prize in 2010 and past projects include the Rolex Learning Centre in Switzerland and the Louvre Lens gallery in France.
Photography is by Iwan Baan.