# Fresh pork loin tonkatsu and mazeudon at Kosi, a Seongsu udon spot - By Yihyeon (https://superchart.com/en/@seoul-supper-index/) - Written Sep 5, 2026 - Updated Sep 15, 2026 - Local places › Restaurants › Seongdong, Seoul - Sponsored: This visit was sponsored by the business. - English edition: https://superchart.com/en/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/ - Also in: [한국어](https://superchart.com/ko/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [日本語](https://superchart.com/ja/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [简体中文](https://superchart.com/zh-cn/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [繁體中文](https://superchart.com/zh-tw/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [Tiếng Việt](https://superchart.com/vi/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [ไทย](https://superchart.com/th/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [Bahasa Indonesia](https://superchart.com/id/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [Bahasa Melayu](https://superchart.com/ms/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) · [Español](https://superchart.com/es/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/index.md) ## In short Kosi Seongsu Branch is a tonkatsu and Sanuki-noodle udon restaurant on Sangwon 1-gil in Seongsu, Seoul. A regular who first came back for the chewy udon noodles ordered the fresh pork loin tonkatsu and Sanuki-noodle mazeudon (mixed-sauce udon), plus a sweet potato cheese croquette given through a review event. Crisp breading, loin with no tough bits and springy noodles that cling to the sauce earned Kosi Seongsu Branch a five-star return-visit rating. ## Good to know - **Ordered**: Fresh pork loin tonkatsu, Sanuki-noodle mazeudon - **Review event**: Sweet potato cheese croquette provided - **Location**: 31 Sangwon 1-gil, 1F, Seongdong-gu, Seoul (near Ttukseom Station and Seoul Forest) - **Would visit again**: Five stars *as written by the visitor on Sep 5, 2026* ⭐️⭐️⭐️ Introducing a restaurant I genuinely, truly love and go back to again and again ⭐️⭐️⭐️ A place I almost want to keep to myself! You really have to try this one!!! Kosi Seongsu Branch is where I always go whenever I'm craving tonkatsu (breaded pork cutlet) in Seongsu. I originally loved this place for its chewy cold udon noodles, but after trying the pork loin tonkatsu, the cutlet won me over too. The outside is properly crispy, but the meat inside was way more tender than I expected — I think Kosi will be my first thought for tonkatsu in Seongsu from now on. ## Where Kosi Seongsu Branch is and what we ordered Kosi Seongsu Branch is a tonkatsu and udon restaurant at 31 Sangwon 1-gil, 1F, Seongdong-gu, Seoul, near Ttukseom Station and Seoul Forest. This time I had the pork loin tonkatsu, Sanuki-style mazesoba udon, and a sweet potato cheese croquette that came through a review campaign. ![Storefront of Kosi Seongsu Branch](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-01-4d4gj-1200.webp) ![Operating hours signage at Kosi Seongsu Branch](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-02-1etdp-900.webp) ![Interior and seating at Kosi Seongsu Branch](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-03-f4hv7-900.webp) ![Table set with pork loin tonkatsu and mazesoba udon](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-04-181xb-900.webp) ![The ordered tonkatsu set meal](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-05-qmxjk-900.webp) ![A bowl of Sanuki-style mazesoba udon](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-06-11atv-900.webp) ![Table with the review campaign's sweet potato cheese croquette](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-07-sm123-900.webp) ## Fresh pork loin tonkatsu: the dish to order in Seongsu From the very first cut, I could tell the meat quality on Kosi Seongsu Branch's pork loin tonkatsu was good. ![Cross-section of the sliced pork loin tonkatsu](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-08-146tl-900.webp) ![Crispy-breaded pork loin tonkatsu](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-09-1cnwg-900.webp) ![Close-up of the tonkatsu meat cross-section](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-10-1aomq-900.webp) The breading stayed properly crispy while the meat inside was really tender. I expected some chewiness since it's loin, but I barely noticed any tough parts — the more I chewed, the juicier and cleaner the flavor got. ![A piece of pork loin tonkatsu lifted up](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-11-r2ygr-900.webp) What I loved most was the contrast between the outside and inside textures. Crisp on the outside, then straight into tender loin. The meat must have been prepped well, because there was no dry or tough feeling at all — I could eat it comfortably all the way through. I originally went to Kosi for the udon, but after this cutlet, my thinking's shifted a bit. When I'm craving tonkatsu in Seongsu, I think I'll come back here. ![Tonkatsu dipped in sauce](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-12-dubrl-900.webp) ## Sanuki-noodle mazeudon: how chewy are the noodles? What I like most about Kosi Seongsu Branch is still the udon noodles. Mazesoba udon (sauce-tossed udon) is a dish where you mix the sauce and meat evenly through the noodles, and the sauce here is rich and savory while clinging well to the noodles. It leans more toward umami than intense spice, so it wasn't overwhelming to eat alongside the tonkatsu. ![Sanuki-style mazesoba udon before mixing](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-13-1og8x-900.webp) ![Mazesoba udon topped with meat and sauce](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-14-1b6fp-900.webp) Being handmade noodles, you can really feel the springy, chewy bounce. Even with a rich sauce, the noodles hold their own presence and get chewier the more you chew — this is exactly why I love Kosi's udon. ![Noodles lifted from the mazesoba udon](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-15-1lwk3-900.webp) ![Mazesoba udon served with kelp vinegar](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-16-ot0ct-900.webp) Adding a splash of kelp vinegar partway through brings a refreshing lift and changes up the flavor. Once you've eaten most of the noodles, mixing rice into the leftover sauce makes for the perfect finish. ## The review-event sweet potato cheese croquette I also received a sweet potato cheese croquette through the review campaign. Ordering the tonkatsu and mazesoba udon together let me alternate between the crispy dish and the chewy noodles, and with the croquette added, the whole meal felt pretty filling. ![Sweet potato cheese croquette received through the review campaign](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-17-71bd1-900.webp) ## Why we keep coming back to Kosi Seongsu Branch I originally loved this place for the chewy udon noodles, but this time the pork loin tonkatsu left a bigger impression than I expected. I loved the contrast between the crispy breading and tender loin, and above all, being able to eat it comfortably with no tough bits was exactly my thing. The mazesoba udon was great too, with noodles that had real bounce. ![A full meal with tonkatsu and mazesoba udon together](https://img.superchart.com/images/koshi-seongsu-mazeudon-pork-cutlet/koshi-seongsu-mazeudon-pork-cutlet-18-1vuwz-900.webp) If you're near Seongsu or Seoul Forest looking for a good tonkatsu spot and want udon alongside it, Kosi Seongsu Branch is worth checking out. I'll probably come back next time I'm craving tonkatsu :) Return visit intent: ⭐️⭐️⭐️⭐️⭐️ ## Where it is - Kosi Seongsu Branch (코시 성수점) - 31 Sangwon 1-gil, 1F, Seongdong-gu, Seoul, South Korea - 서울특별시 성동구 상원1길 31 1층 - 37.5464155, 127.0474867 - Google Maps: https://www.google.com/maps/search/%EC%BD%94%EC%8B%9C%20%EC%84%B1%EC%88%98%EC%A0%90/@37.5464155,127.0474867,17z --- Superchart · https://superchart.com/en/@seoul-supper-index/koshi-seongsu-mazeudon-pork-cutlet/ · https://superchart.com/llms.txt