Mori Kei is a Japanese fashion style that intends to capture how someone living in the woods may dress. In Japan, the style is generally referred to as Mori Girl ( 森ガール ) or Mori Boy, ( 森ボーイ ) depending on the gender of the wearer and not Mori Kei (森系, meaning "forest types").

In 2006, a community called "Mori Girl" was created on the Japanese social network Mixi . The name was chosen by its manager, Choco, after a friend commented on one of her outfits stating "You look like you are in the forest."

The “Mori Girl” Mixi community reached 35,000 people in 2009, and it caused a big boom that led to the creation of multiple mori kei magazines and brands, such as Mori Girl Lesson magazines, Choco's Mori Girl Book, and the popular mori brand Wonder Rocket. The style also saw considerable popularity overseas, where the name Mori Kei began to be used, leading to the creation of various communities on social media and . However, in Japan, the style began to decline in the early 2010s, and magazines and brands declined with the end of its popularity.

As of 2019, the online Mixi group where mori kei originated has been deleted, and the brand "Wonder Rocket" closed its Harajuku store in 2017.

The heyday of the fashion may have passed, but because there still is a number of enthusiasts, mori kei itself has not disappeared. There are still brands catering to mori kei, even though the design has changed to suit the present, as well as the still-existing international online community.

Mori Kei has undergone many changes and trends since the height of its popularity, but the basic appearance still remains the same. It combines clothing that appears natural, girly, layered, and loose. In general, the main staple of mori fashion is its many loose layers that hide the body shape, and the term "yurufuwa" (ゆるふわ) is often used to describe its fluffy appearance.

Clothes with embroidery, various kinds of lace, and light materials are preferred and for layering, cardigans, vests, and knit scarves and shawls are often used in the style. Besides its most known off-white color schemes, earth tones and other natural tones, such as navy blue, khaki, beige, and brown are used. Floral colors such as light pinks and blues are also sometimes used. Popular accessories include lace-up leather boots, tights, and baskets.

The hair and makeup match the outfits in their natural appearance. The popular eye shadow options are beige, gold and pink, in minimal styles. The blush is often highly placed and round. The eyebrows are thick and natural.

While Mori Kei is not a music genre, some Japanese bands briefly identified themselves as Mori Kei during the style's heyday. Additionally, genres like folk, baroque pop, and dream pop are popular in the community.

Dark Mori (also known as Mori Goth, or originally Black Forest Mori) takes the standard Mori Kei aesthetic, but gives it a gothic twist, incorporating darker clothing into the look compared to the usually more light-hearted Mori Kei. The style was created by the international community and part of it later separated off into Strega /Witchcore.

Today, Dark Mori itself is considered separate from Strega , as it still follows the rules of the original Mori Kei in terms of layering and shape. Many people in this aesthetic consider Helena Bonham Carter to be a style inspiration. They are also more open to Goth music and the Goth community (particularly the Strega aesthetic and the work of Siouxsie and the Banshees and All About Eve).

This substyle has continued to grow in considerable popularity amongst the international community and is widely known.

Natural Kei is a subgenre of Mori Kei which is generally understood to be a more simple, or even casual, version of it. Natural Kei also takes inspiration from American styles such as Prairie and Western , and 1970s brands such as Gunne Sax and Laura Ashley.

The term Natural Kei originated in the 1980s (or possibly earlier) as a way of describing the style associated with Japanese brand PINK HOUSE. At this time, it had a particular silhouette to it, and focused mostly on layered skirts, pinafores, and sometimes brighter colors than Mori Kei, and at times resembled Country Lolita.

However, in the modern era, Natural Kei has evolved to include more casual clothing items, solid colors, and has less emphasis on a particular silhouette. Online, it is often misused as an umbrella term for all comfortable, feminine Mori-inspired outfits on earth tones.

Hama Kei is a substyle of Mori Kei adapted to life in the seashore and the beach that gained temporary popularity in the 2010s. It features fewer and lighter layers, often shorter skirts and sleeves, and an emphasis on blue, aqua, beige and white tones, as well as the use of denim and sailor-like stripes and anchors.

Yama Kei was introduced by Japanese women with a passion for the outdoors. It features practical outdoor clothing and equipment in bright colors and vivid patterns.

Bright Mori is a subgenre that utilizes bright or pastel colors, and more Kawaii motifs. It is believed to have been coined by icewindandboringhorror on Tumblr in 2014.

Bright Mori takes influence from more colorful fashion styles such as Fairy Kei , Cult Party Kei , and Dolly Kei , although still emphasizes the Mori Kei silhouette, and its characteristic layers of thin fabrics and lace. Bright Mori is also generally the only form of Mori Kei where unnaturally colored hair and wigs are common. While it had a decent following in the mid-2010s, the aesthetic never reached the heights of popularity that other Mori substyles have, and remains obscure today.