Type A: Yukata
Brightly-coloured yukata that are obtained by beating Normal Mode. Mio's is pink, and Mayu's is blue. Despite being in a poor, terrifying village, this costumes make it seem like they're visiting a haunted house attraction at a theme park.
Type B: Yukata 2
These, too, are obtained by beating Normal Mode. These are dark, subdued yukata. Mio's is navy with a white obi, and Mayu's is black with a butterfly pattern and deep red obi. The obi is tied around her back like a butterfly. The two of them look quite grown up.
Type C: Mini Yukata
Obtained by beating Hard Mode. These are short-sleeved yukata that have been popular in recent years, too. Mio's is green and Mayu's is pink. Note that their legs are bare. Their shortness makes it seem like the scariness would diminish quite a bit.
Type D: Twin Shrine Maiden Kimono
These are also obtained by beating Hard Mode. Mio wears Yae Kurosawa's costume, and Mayu wears Sae Kurosawa's. Both wear the same design and colour of kimono, but Mayu's has bloodstains that start below the cchest. This alone will make things quite a bit scarier.
Type E: Differently-Coloured Everyday Outfits
Obtained by clearing Mission Mode with all S ranks. The design is the same as their normal outfits, but the colour scheme is different. The biggest difference for both Mio and Mayu is their socks. This colouring is the same as that of Miku, the heroine of Fatal Frame.
Type F: School Uniform
Obtained by clearing Mission Mode with all S ranks. This allows you to play with a different taste to the everyday outfits. Take note of their matching red checked pleated skirts and the bandage on Mayu's kneecap. Their not wearing baggy socks also gives them a good impression.
Type G: Goth loli
Obtained by beating Mission Mode. This costume is like that of a woman from the Middle Ages, using an abundance of lace. Gothic lolita. It doesn't match the worldview at all, but maybe it matches with an old Japanese house?
Type H: Leather
Obtained by beating Nightmare Mode. This is a sexy costume that doesn't really need much explanation. Mio's is black and Mayu's is red. Notice the weaving on their chests and their exposed stomachs. Their hair also seems to be dyed in more ashy tones.
Mio's are obtained by beating Normal Mode, and Mayu's by beating Mission Mode. They both have the same design. By the way, they're also present during cutscenes, so people who want to take a good look at their glasses-wearing faces should check this out.