Seongsu restaurant for tonkatsu and cold udon: Kosi
In short
Kosi Seongsu Branch is a Japanese restaurant in Seongdong, Seoul, near Ttukseom Station. I ordered tempura bukkake udon, half-and-half katsu, shrimp tempura, and lotus root kushikatsu for a satisfying mix of cold noodles and crisp fried dishes. Kosi Seongsu Branch is a great stop for a hearty Seongsu date meal.

Good to know
- Location
- 9-9 Seongsu-dong 1-ga, Seongdong-gu, Seoul
- Hours
- Daily 11:00–21:00
- Break time
- 15:00–17:00
- Ordered
- Tempura bukkake udon, half-and-half katsu, shrimp tempura (2 pieces), lotus root kushikatsu (3 pieces)
as written by the visitor on Sep 11, 2026

Today, I’m introducing a place I visited because I wanted to have tonkatsu and udon together in Seongsu. There are so many great places to eat in Seongsu that I had a hard time deciding, but that day I went to Kosi Seongsu Branch (코시 성수점), where you can enjoy Japanese-style tonkatsu and udon together. Especially when the weather is hot like it has been lately, you keep craving cold udon rather than warm udon, right? So I properly ordered a tonkatsu dish along with bukkake udon and enjoyed it all!
How long does it take to get to Kosi Seongsu Branch from Ttukseom Station?
Kosi Seongsu Branch is about a two-minute walk from Exit 6 of Ttukseom Station. It is close to the station, so it seemed convenient for meeting up, too.
The exterior and atmosphere inside

This is the exterior of Kosi, a Seongsu spot known for tonkatsu.

There was a waiting list in front of the restaurant. We visited near the end of lunch hours and luckily got in right away, but it seems there is often a wait at weekday lunch.


As soon as we stepped inside, it had such a neat Japanese restaurant feel. It was tidily arranged but still atmospheric, giving it that proper Seongsu dining-out vibe.

We took seats at the bar table.

Water and sauces were set out at every seat, and ordering through the kiosk was easy, so the whole ordering process was simple.
Kosi Seongsu Branch menu


Here is the menu at Kosi Seongsu Branch.
Ordering tempura bukkake udon and half-and-half katsu
- Tempura bukkake udon
- Half-and-half katsu
- Shrimp tempura (2 pieces)
- Lotus root kushikatsu (3 pieces)

Tempura bukkake udon and lotus root kushikatsu

Half-and-half katsu and shrimp tempura

Tempura bukkake udon that was perfect for a hot day
First, the tempura bukkake udon that I especially enjoyed that day! It is cold udon topped with crisp tempura. It was absolutely perfect for a hot summer day.

First, pour in the cold broth.


The cold, springy udon noodles were amazing! They were bouncy and chewy, so you could feel the noodles’ elasticity with every bite. Served cold, the broth tasted clean, and it definitely felt lighter in hot weather.

The lotus root kushikatsu (skewered fried cutlet) was on the soft side! I expected fried lotus root to be firm and crunchy, but it was soft. As I chewed, its nutty lotus-root flavor came through, and it was nice.

Half-and-half katsu with pork loin and cheese
The half-and-half katsu lets you enjoy pork loin katsu and cheese katsu at the same time.

The cheese tonkatsu was packed with cheese. This is exactly the look you want from cheese tonkatsu >,<

I topped the crisp pork loin tonkatsu with sauce and wasabi, yum~~ As you would expect from a place known for tonkatsu in Seongsu, the crisp coating and the pork loin’s chew were something else.

The cheese tonkatsu was even tastier with the cheese’s soft, rich nuttiness, haha. The cheese tonkatsu was more my style.


Adding shrimp tempura to bukkake udon
The extra shrimp tempura was a great pairing with the bukkake udon, haha. After eating cold noodles continuously, having warm, crispy shrimp tempura in between changed up the texture completely, which I loved. I definitely recommend adding it as a side~~
My overall thoughts on Kosi Seongsu Branch
Kosi Seongsu Branch is a good place to visit when you want tonkatsu and cold udon together. The fresh pork loin half-and-half katsu was nice because I could try both the classic katsu and cheese katsu at once, while the tempura bukkake udon was satisfying with chewy noodles and crispy tempura. It is also close to Ttukseom Station, making it a lovely Seongsu tonkatsu spot for a filling meal during a date in Seongsu~~
Where it is
31 Sangwon 1-gil, Seongdong-gu, Seoul, South Korea서울특별시 성동구 상원1길 31 1층







