A grey knit fabric notebook cover holding a habit tracker and two pens on a wooden surface.

Midori Just Gave Your Planner a Sweater: A look at the Cute & Quirky “Notebook Belly Warmer”

Shirogane

September 29, 2026

New Product

Stationery

For those who don't know what a belly warmer is, in Japan, the haramaki (腹巻き) is traditional knitted thermal band worn snug around the stomach to retain core body heat. It's a staple of everyday winter comfort. It's not so common in the west, but if you give it a try, you'll never go another fall or winter without it again.

Japanese actor Kiyoshi Atsumi wearing a light blue shirt, brown fedora, and traditional haramaki belly warmer. — The late legendary Japanese actor Kiyoshi Atsumi sporting his iconic look with his haramaki in "It's Tough Being a Man" (男はつらいよ)

Stationery pioneer Midori looked at that cozy concept and asked an unexpected question: why shouldn't our notebooks get the exact same treatment?

Midori officially rolled out the latest edition of its cult-favorite Notebook Belly Warmer (Techo no Haramaki / 手帳のはらまき) on September 25, 2026. Part protective notebook sleeve, part expandable organizer band, and part old-man stomach sweater, the accessory wraps around your daily planner to keep it securely shut while providing built-in exterior pockets for pens, washi tape, smartphones, and even snacks!

To pull off a product that slips on and off effortlessly without losing its shape, Midori partnered with Gosen Knit (五泉ニット), a premier textile brand hailing from Gosen City in Niigata Prefecture, a region with over 250 years of textile heritage. Known across Japan for top-tier craftsmanship. Gosen knitwear provides exceptional stretch, durability and softness, rather than the typical scratchy wool. The band uses a smooth, dry-touch cotton-acrylic blend that stays comfortable in hand across all four seasons.

Midori journal cover featuring a blue and white ribbed Gosen Knit fabric texture held by a hand. — Midori's adopted Gosen Knit (五泉ニット) material for their journal cover design *(Source: https://www.designphil.co.jp/)*

Even better, the sleeve is fully machine-washable, so you don't have to stress about tossing it into a tote bag or surviving the occasional coffee splash. Midori simply recommends popping it into a laundry net, skipping the tumble dryer, and letting it hang dry in the shade to keep its shape. Though they do note that it may shrink slightly due to the nature of the fabric, so just keep that in mind.

A Fan-Voted Color Champion

The big story for this season’s drop is the arrival of Denim Blue.

At the massive annual Stationery Girls’ Expo 2025 (Bungu Joshi Haku 2025 / 文具女子博2025), Midori held an on-site user vote asking attendees to select their dream colorway for the next production run. The clear winner took the top prize: a rich, heathered blue knit inspired by faded indigo denim. It officially debuts this season in a classic, cozy cable knit alongside returning and two-toned styles.

The popular "Denim Blue" - Winner of the Stationery Girls' Expo 2025 (文具女子博2025) (Source: https://www.designphil.co.jp/)

Elastic Comfort With Pocket Utility

Woven from a soft, durable cotton-acrylic knit, each Techo no Haramaki acts as an elastic tube that stretches neatly across standard book formats from A6 up to B6. The upper cuff folds over the top or functions as a quick-stash pocket, while dedicated slip compartments along the front keep your favorite writing tools firmly attached to your journal without stretching out leather covers or snapping elastic bands.

Blue ribbed knit fabric journal cover with a front pocket holding pens and stationery items. — The journal cover folds over itself protecting your pens, tools, or smartphone and preventing any unwanted stationery spills *(Source: https://www.designphil.co.jp/)*

The collection spans six distinct color options across three textured knit patterns:

Cable Knit (ケーブル編み): The fan-favorite textured weave, available in delicate Baby Pink and the brand-new award-winning Denim Blue.

Ribbed Knit (リブ編み): Clean, vertical-ribbed duo-tone designs in Mint × Grey and Pale Blue × Navy.

Random Ribbed Knit (ランダムリブ編み): Contemporary alternating ribbing in vibrant Lime Yellow and deep Bordeaux.

Cable knit journal covers in Baby Pink and Denim Blue featuring a textured vertical pattern. — The cable knit journal cover in Baby Pink (left) and Denim Blue (Right) *(Source: https://www.designphil.co.jp/)*

Four variations of rib knit journal covers in mint, gray, light blue, and navy blue textures. — The rib knit journal cover in Mint & Gray (Left) and Blue & Navy (Right) *(Source: https://www.designphil.co.jp/)*

Rib knit fabric texture shown in lime yellow on the left and deep bordeaux on the right. — The random rib knit in Lime Yellow (Left) and Bordeaux (Right) *(Source: https://www.designphil.co.jp/)*

Where to Find the Haramaki For Your Journal Notebooks

If you’re looking to step away from the typical black or brown leather cover for your journals, these cozy covers turn any plain journal into a tactile desk companion. You can pick up the entire lineup directly from Midori’s official online store at midori-store.net as well as select stationery boutiques across Japan.