Bento box review: Atsuben Kun heats up your lunch

As I have said often on these pages, bentos are usually filled with food that is supposed to taste good at room temperature. But there's no denying that sometimes we want our lunch to be hot, or at least warm. There are various ways to make sure this happens of course, from using a microwave (if you have access to one) or carrying your lunch in a thermal lunch jar and/or an insulated bag. The Atsuben Kun bento box takes the warm bento lunch a step further: it actually heats up your bento within the box itself.

From the outside, the Atsuben Kun looks like a regular bento box. It's very sleek, and the white plastic feels very nice.


The logo is very cute - the "u" of At(s)uben is a litle steamy pot. (The "atsu" or "atu" part of the name means hot,"ben" is short for bento, and "kun" is just an informal, affectionate suffix for a name, usually used when addressing a young man or boy.)


The Atsuben Kun reveals its secret when you look at the base. It has power input...


...for the bottom section, which contains a ceramic heater, similar to the ones you see in space heaters. (The warning label in Japanese says to not touch it when it's plugged in or while it's still hot.)


Here's what's in the the Atsuben Kun package. It looks like a three-tier box from the outside but it's actually two-tier box with the bottom tier being the heater. The top compartment has a leak-resistant flexible plastic lid. There's also a power supply for Japanese electric outlets.


The power supply has 100/110V-220/240V / 50-60Hz input and 3Amp / 8V output, so you should be able to use it just about anywhere in the world. You can use Japanese plugs as-in most U.S. outlets, though if you are not sure you can get an adapter plug. In Europe and many other places you will need an adapter plug, which is not included (the one shown in the pic is for France) - they are cheap and easy to get at any electronics store. You can also order the Atsuben Kun with a cigarette lighter car power plug instead.


I tested how well this thing worked with a real bento! I filled it up with fairly standard (for me) bento foods: rice in the bottom section with a little furikake on top, and the other foods in the top compartment (Miso marinated pork, Easy sugarfree carrot kinpira, some steamed broccoli to fill the gaps, and tamagoyaki). I put the rice in the bottom compartment because I wanted it to get the warmest. Then, I put the 2 sections filled with food in the refrigerator for about 8 hours. This was to simulate a typical scenario where I can see this bento box being used - you make the bento and fill it up the night before, pack it with an ice pack in the morning (in an insulated bag to really keep things cool) and heat it up before lunch.


I re-assembled the Atsuben Kun and plugged him in, and set my timer for 70 minutes as per the Japanese instructions.


So did it heat up from refrigerator-cold to hot in 70 minutes? Not quite. It was warm enough to be pleasant, but not hot. Probably if you heated it up from room temperature 70 minutes would be enough. Anyway, no big deal - I gave it another 20 minutes.


After the additional 20 minutes, the rice in the bottom compartment was actually hot! It almost tasted like freshly cooked rice. The top compartment doesn't really get hot since it is not in direct contact with the heating element, just warmed up a bit from the little steam rising from the food in the bottom compartment. But that's enough really to have a warm-bento experience. I really enjoyed it!


Best uses, and pros and cons

I think this bento box is great for people who don't have access to a microwave at lunchtime, but still want a warm lunch experience. With the cigarette lighter power plug, you could even heat up your bento on the go! (Personally I think I'd order the box with the cigarette lighter plug and get the house-current one separately, if I needed to use this in my car.) It doesn't draw much power (the instructions say it consumes about .6 yen per use - and electricity in Japan is expensive), and is quite unobstrusive.


  • Enables you to have a warm lunch without access to a microwave
  • The food in the bottom compartment gets really hot
  • Compact and relatively lightweight, despite the heating element
  • Uses very little energy
  • The food container parts are dishwasher safe (Handwashing recommended for the outer lid; the heating plate element should only be wiped clean)
  • Sleek, cool design; feels very well made and durable
  • Ups your geek factor!


  • Pricey (5700 yen, or about about US $70 / €53 - use the handy currency converter on the order page for the current price. Gotta love those exchange rate fluctuations!)
  • A bit heavier/bulkier than a regular bento box of that size because of the heating element, though still very portable
  • On the small side (580ml total capacity; good if you're doing portion control though)
  • Only the bottom compartment gets really hot; the top compartment gets lukewarm
  • Takes a bit of preplanning so your bento is as hot as you need it to be by lunchtime (about 70 minutes from room temperature; add 10-20 minutes if your bento is refrigerator cold)


  • Remember to always put the food you want to be really hot in the bottom compartment. In the Japanese video posted on the product page, they show it being used by putting curry stew in the bottom compartment and rice on the top.
  • The top compartment does heat up a little bit, so any food you want to keep cool like a side salad or fruit should be packed in a separate container.
  • Use a timer as I did. There's no automatic shutoff.
  • Eating utensils are not included, so add your own.
  • To carry the Atsuben Kun, I'd recommend using a furoshiki cloth (here's how to make your own; you can also use any square cloth, like a bandanna) or an elastic bento belt to, hold all those layers plus the lid together. The Atsuben Kun doesn't come with its own belt, so use one you already have from another box, make your own from wide elastic, or order one here.

To sum up: I think this is a very cool box that is sure to draw comments at the office. If you yearn after a hot bento at lunchtime, especially if you like making your bento the night before and sticking it in the fridge, this may be just the box for you.

The Atsuben Kun is available from Bento&co.

(Disclosure: This product was supplied to JustBento by the vendor for review. I was not compensated in any way for the review, and the opinions expressed are my own.)

(I have a whole bunch of other cool bento product reviews coming up. Stay tuned ^_^!)

Last modified: 
11 Jun 2019 - 06:19

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