Dongjak Japanese restaurant for mixed tonkatsu: Kosi Isu Branch

Kosi Isu Branch near Exit 9 of Isu Station

I spent ages wondering what to have for dinner near Isu Station. It was still hot out, and all of a sudden I was craving refreshing cold udon rather than a steaming bowl of soup. But udon alone felt a little lacking, so this time I went somewhere that also serves tonkatsu (Japanese pork cutlet), haha.

That place was Kosi Isu Branch. It is close to Exit 9 of Isu Station, so it was easy to find, and I loved the menu right away because I could have handmade udon and tonkatsu together.

Location and the menu outside

Kosi Isu Branch is on the first floor of the Isu Xi building. It is just a short walk from Exit 9 of Isu Station, so getting there by public transit was pretty convenient. You can also use the building's underground parking, with one hour of free parking support. Worth noting if you are driving.

The menu and prices were displayed in front of the restaurant, so it was nice to look over what to order before going in.

A comfortable interior for solo dining, too

Inside, the overall atmosphere was clean and tidy.

It is not a huge restaurant, but there are seats for eating alone, so it looked easy enough to come by yourself.

In particular, each table has a tablet for ordering, so you can take your time choosing without having to call over a staff member,

then order and pay all at once. I find this kind of setup quietly convenient these days, haha.

Ordering ten bukkake udon and mixed tonkatsu

You could say udon and tonkatsu are Kosi's signature dishes. From handmade udon to a range of tonkatsu options, the menu lets you choose according to your taste.

There were so many kinds of tonkatsu that I debated what to get, then ordered the mixed tonkatsu so I could enjoy two varieties at once. And the dish I most wanted to try that day! Of course, ten bukkake udon too, haha. I even added king shrimp katsu as a side! I wanted to try everything one by one, but when the food arrived, I thought I had done well ordering it this way, lol.

Ten bukkake udon noodles and tsuyu

The dish I was most looking forward to that day was the ten bukkake udon. On hot days, instead of hot udon,

I find myself more drawn to cold udon that is refreshing and clean-tasting.

Maybe because the noodles were made in-house, they had quite a chewy bite.

Eating the chilled udon noodles with tsuyu (Japanese dipping sauce), I could really feel that springy texture.

The noodles especially had not gone soft and still had plenty of bounce, so I loved how pleasantly chewy they became with every bite, haha.

True to ten bukkake udon, it came topped with crisp tempura, so the savory fried flavor alongside the cold udon made it feel more substantial than simple cold udon. The tsuyu was salty and full of umami, and it seasoned the chewy noodles really well.

Above all, it was cold and refreshing, just right for a hot day. Having bites of tempura in between added a crisp texture, and I enjoyed it all the way through, haha.

Mixed tonkatsu with salt and wasabi

Next up was the mixed tonkatsu I ordered!

Rather than eating just one kind of tonkatsu, I wanted to try two flavors together, so I ordered the mixed plate—and it was quietly a great choice. The breading was crisp overall, and the meat was thick, making even one piece feel pretty filling.

Since it came as a mixed plate, it was fun comparing the two varieties, and it was easy to keep eating without getting tired of it. The combination of crisp breading and tender meat was good, and I could really taste that characteristic savory richness of tonkatsu.

It was tasty dipped in the standard tonkatsu sauce, but personally, I also recommend salt with wasabi! A little salt and a bit of wasabi on a piece of tonkatsu seemed to bring out its savory flavor even more, haha. Add a little pepper too, and it cuts through the richness, so several pieces do not feel too heavy. And with the mixed plate, it was more fun because I could alternate between the two flavors depending on what I felt like eating.

Udon and tonkatsu together on a hot day

After eating at Kosi Isu Branch, the ten bukkake udon I had been looking forward to was my personal favorite. The chewy, springy handmade udon noodles with cool tsuyu and crisp tempura made for the kind of clean, refreshing meal I crave on a hot day.

Having the mixed tonkatsu alongside it made the meal much more filling than having just one dish. I also personally loved being able to enjoy two tonkatsu varieties at once by ordering the mixed plate, haha. If, like me, you want udon and tonkatsu, do not give one up—just order both, lol. Especially in hot weather like this, cold ten bukkake udon and crisp tonkatsu turned out to be such a good pairing.