Seongsu lunch for two at a katsu and udon restaurant: Kosi Seongsu

Why we chose Kosi Seongsu Branch for lunch in Seongsu

I ended up at Kosi Seongsu Branch while hunting for a lunch spot in Seongsu. There are so many good restaurants in Seongsu that it's hard to choose, but this place caught my eye because the menu looked a little unusual. After actually eating there, I was way more satisfied than I expected. The cold udon and cheese katsu I had that day were especially memorable — I still think about them.

At first I wasn't sure cold udon and tonkatsu would go well together, but once I tried them side by side, they matched surprisingly well. It's not a combination you see often, which made me even more curious, and both dishes turned out to have their own distinct charm.

Cold udon at Kosi: springy noodles in chilled broth

I started with the cold udon, and it's honestly one of the dishes from that day that stuck with me the most. Udon usually brings to mind warm broth, so the cold version felt different from the very first bite. The cold broth and the bouncy udon noodles went really well together, and the whole thing felt very clean in the mouth, with a nicely chewy noodle texture.

Cold udon can easily end up bland or flat, but the flavor balance here was better than I expected, so I kept going back for more. The cold broth also kept my palate feeling clean bite after bite, and I thought it would be perfect on a hot day. If you're already a fan of udon, this is a dish worth trying at least once.

Cheese katsu tastes best while it is still hot

And then the cheese katsu we ordered alongside it!

I thought tonkatsu was a familiar enough dish, but this one was much better than I expected too. Cutting into the crispy fried cutlet reveals cheese inside, and eating it while still warm meant the cheese was softly melted — genuinely delicious.

Crispy on the outside, moist inside, with the nutty, soft flavor of melted cheese layered on top — it had a different appeal from a regular tonkatsu. I especially liked feeling the crunchy texture of the katsu together with the softness of the cheese.

With the first bite, the crispiness hits first, and then the savory cheese flavor follows right after — I love that kind of combination, so I really enjoyed it. The tonkatsu itself wasn't overly greasy either, which made it easy to pair with the cold udon.

Eating the cold udon and cheese katsu in turn

Honestly, what I liked most about Kosi that day was that the menu wasn't ordinary. The cold udon and cheese katsu combo itself was already interesting, but once I tried it, it wasn't just a novelty — the taste was genuinely satisfying too, which made it stick in my memory even more.

Taking a bite of cold udon and then the cheese katsu, the clean chewy feel of the cold udon and the crispy, savory taste of the katsu kept alternating, almost like they were covering for each other's weak points. Eating tonkatsu alone for too long can get a bit greasy, but the cold udon kept that in check, so I could eat happily all the way to the end.

Seongsu has plenty of places serving similar dishes, and plenty of already-famous restaurants too, but I felt good about choosing something a little different this time.

Coming as a pair? Order one of each and share

I like trying new dishes, so maybe that's why Kosi's cold udon left such an impression. It felt different from the udon I usually know, so I was curious how it would taste at first, but after trying it myself, I understood why people seek this dish out.

The cheese katsu also exceeded my expectations. Tonkatsu is such a familiar dish that I ordered it without high expectations, but the crispy batter with soft cheese inside made it genuinely delicious. It was best eaten while the cheese was still melted and warm.

If you're visiting with one other person, I'd recommend doing what we did — order one cold udon and one cheese katsu and share them. The two dishes have such different styles that alternating between them is fun, and eating both together means you won't get tired of either one all the way through.

What stuck with me most about eating at Kosi Seongsu Branch this time was really that sense of 'unusual, but delicious.' Often when food is just unusual, it's a one-time try and that's it, but here the menu itself was different and the taste was good too, so it's a place I keep thinking back to.

The cold udon in particular had a clearly different charm from the udon I usually eat, and the cheese katsu was satisfying too, with the crispy cutlet and savory cheese working well together.

If you're craving something a little different in Seongsu, or just want new food instead of the usual, Kosi Seongsu Branch could be a good choice. This was my first visit, and the cold udon especially stayed with me, so I'd love to try it again next time I'm in Seongsu.

Kosi Seongsu Branch let us enjoy familiar tonkatsu alongside slightly unusual cold udon. What made that day's meal stand out wasn't just that it tasted good, but that it made me think, 'oh, this combination works too.'

If you're looking for a good meal in Seongsu, give it a try. I'd especially recommend it to anyone who likes udon. After eating here, I feel like I really got to know the appeal of cold udon, and next time I'd like to try other menu items too.