Tonkatsu with kelp vinegar in Dongjak, Seoul: cheese katsu at Kosi Isu

I had an errand near Isu Station, so I stopped by Kosi Isu Branch, a well-known tonkatsu spot, for cheese katsu and mazesoba udon (mixed udon noodles). Let's get right into the review~

Where is Kosi Isu Branch, and what are its hours?

Kosi Isu Branch is on the 1st floor of 300 Sadang-ro, Dongjak-gu, Seoul. It's open daily from 11:20 to 21:00, with a break time from 15:20 to 17:00, and last order at 14:50 and 20:30.

Kosi Isu Branch is right in front of Exit 9 of Isu Station, so it's very easy to reach by public transit. But Exit 9 is currently under construction, so you'll need to come out through Exit 8 instead — it's still only about a 3-minute walk from there.

Parking at Kosi Isu Branch

If you use the building's parking lot, you get 1 hour free. I came by public transit, but it's nice to know there's parking support even in Seoul — that makes driving there pretty convenient too.

Ordering cheese katsu (12,500 won) and mazesoba udon (11,000 won)

There's a menu posted outside too, so it was easy to decide what to order before going in. The country-of-origin labeling was also clearly displayed. I ordered the cheese katsu (₩12,500) and the mazesoba udon (₩11,000). I liked that the prices weren't too high either.

Weekday lunch at Kosi Isu Branch: is there a wait?

I visited during weekday lunch, and the place was really packed, probably with office workers from nearby. Still, since there were plenty of tables, there was no separate wait. A lot of people were dining solo too, so it seems like a great spot for a simple solo meal.

Each table had salt, pepper, sesame, shichimi (seven-spice chili powder), and other seasonings already set out, so it was easy to add whatever suited your taste. Enjoying the food as it's served is nice, but I also liked being able to adjust the flavor with a bit of sauce or seasoning to make it my own — especially for adding seasoning or boosting flavor where a dish needed it.

The cheese katsu and mazesoba udon I ordered both arrived. Looking at them again, the crispy cheese katsu and the appetizing mazesoba udon looked hearty and delicious. I especially love salad, so I was really happy that a generous portion of salad came with the meal. Cleansing my palate with the salad between bites of the crispy cheese katsu made the whole meal even more enjoyable.

How was the cheese katsu?

The cheese katsu had a crispy fried pork cutlet packed with savory, soft cheese inside — the first bite stretched into a long cheese pull, impressive in both looks and taste. The crunchy breading, juicy meat, and rich, savory cheese came together really well for a full-bodied flavor. The mild, creamy cheese made it even more enjoyable to eat.

Mazesoba udon with rice to mix in at the end

The mazesoba udon had chewy udon noodles mixed with a savory special sauce, ground meat, and various toppings — full of umami. The sauce soaked well into the noodles, so every bite had a rich flavor, and the savory, slightly spicy kick kept me reaching for more. Plus, after finishing the noodles, you can mix the leftover sauce with rice, which makes for a really filling meal.

Kelp vinegar came alongside the dish so you could add it to taste — having kelp steeped in the vinegar was an unusual and nice touch.

Is Kosi Isu Branch worth a visit?

I'd recommend Kosi Isu Branch, a great restaurant near Isu Station where you can enjoy everything from crispy, savory cheese katsu to umami-packed mazesoba udon and other Japanese dishes. Whether you want a hearty meal or something a bit different, there's plenty to choose from depending on your taste. Plenty of people dine solo here too, so it's a good spot to visit on your own.