Sap Lab Core
2019

Wear something worth staying in.

Sap Lab Core makes women's loungewear and pajamas from satin, brushed cotton, and waffle knit. Designed for the hours you spend at home, not rushing out of it.

v1.02019-01

Yuki Morishita spent seven years as a pattern maker for a mid-size apparel company in Osaka, cutting samples for other people's brands. In the autumn of 2019, after her second child was born, she found herself spending most of her waking hours at home in clothes that were either too stiff to be comfortable or too worn-out to feel good. She started drafting her own patterns on the kitchen table after the kids were asleep. The first brushed-cotton lounge set she made for herself got so many questions from friends that she made twelve more and sold them through a private Instagram account in three days.

Satin weight vs. Fast-fashion average19 momme
Satin Sleep Set. Dusty Rose¥8,900

Button-front top with a relaxed collar and wide-leg trousers in 19-momme satin. The dusty rose colorway is a warm blush with a slight grey undertone. It photographs pink but reads more muted in person. Comes with a matching satin scrunchie.

Satin Sleep Set.…¥8,900

The same 19-momme satin cut in a deep navy that works as well under a robe as it does on its own. The trousers have a wide elastic waistband and two side pockets. A perennial favourite that returns every autumn.

Brushed Cotton Lounge…¥7,400

Heavyweight brushed cotton in a warm oatmeal tone, milled in Aichi. The top is a relaxed crew-neck with dropped shoulders; the trousers have a wide-leg cut and a drawstring waist. Gets noticeably softer after the first three washes.

Updates — Sap Lab Core
Our products

Why women keep coming back

01

Fabrics that feel different

We source brushed cotton from a mill in Aichi Prefecture and use 19-momme satin for our sleep sets. The difference is obvious the first time you put them on.

02

Sizes that fit real bodies

Every piece runs from XS to 3XL. We grade each size individually rather than scaling up from a single pattern, so the proportions stay right across the range.

03

Designed for all-day wear

Our lounge sets move from the bedroom to the kitchen to a video call without looking like you gave up. Elastic waistbands, relaxed cuts, no itchy labels.

04

Seasonal drops, not endless SKUs

We release four small collections a year. Each one is thought through properly. When a colorway sells out, it's gone. We don't restock indefinitely.

News & Announcements

News & Announcements

2026-08-08

How to choose satin pajamas that actually last

Satin pajamas have a reputation for being either luxurious or disappointing, and the difference usually comes down to one number most shoppers never see on the label: momme weight. Understanding it takes about two minutes and changes how you shop for sleepwear permanently.

Read more →
2026-07-16

Caring for brushed cotton loungewear so it stays soft

Brushed cotton is one of the most comfortable fabrics for loungewear, but it's also one of the easiest to ruin in the wash. A few small habits make the difference between a set that lasts two years and one that pills after a month.

Read more →
2026-06-16

Giving loungewear as a gift in Japan: what to consider

Loungewear is one of those gift categories that can go very right or slightly wrong depending on a few small decisions. Here's what's worth thinking through before you order.

Read more →
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With respect

What our customers say

I bought the brushed cotton set in oatmeal and wore it every single day for two weeks. It's the first loungewear I've owned that doesn't look sad after washing.

— Haruka T., Tokyo

The satin sleep set is genuinely the nicest thing I own. I was worried the fabric would be slippery and cold but it's actually really comfortable. The sizing was spot on.

— Mei S., Osaka

Selected client feedback. Individual experiences vary and may not be representative.

19Mm
Momme satin weight
4
Collections per year
7
Fabric families tested before launch
3
Business days to ship
Behind the bench

"Yuki Morishita trained as a pattern maker in Osaka and spent seven years cutting samples for mid-size apparel brands before founding Sap Lab Core in 2019. She launched the brand from her kitchen table after her second child was born, initially selling through a private Instagram account. She still approves every fabric swatch and fit sample personally. Outside the studio, she grows a small container herb garden on her apartment balcony and reads more novels than she finishes."

— Yuki Morishita
Founder, Established since 2019
Hand-finished
Every piece touched by a maker.
Insured shipping
Carrier-insured to your door.
Member of guild
Recognised by trade association.
▲
Direct from maker
No retailer in the middle.
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