Tabelog ratingOimoyasan Koshin is a specialty takeout counter dedicated to one of Japan's favorite traditional snacks: the sweet potato. Located in the bustling B1 food hall of the Daimaru department store, directly connected to Tokyo Station, it's a prime spot for picking up a treat for a train journey or a well-regarded gift.
The main attraction is the daigaku-imo (大学芋), or candied "university potato." Reviewers consistently praise the large, satisfying chunks that retain their fluffy texture beneath a glossy, sticky glaze. The shop often provides the sweet syrup (蜜, mitsu) in a separate pouch, allowing you to add it yourself just before eating. The other signature item is the sweet potato cake (スイートポテト), which fans describe as having an unusually silky, custardy, melt-in-the-mouth texture that sets it apart. For those who want to sample different potato varieties, seasonal tasting sets (食べくらべ) are also available.
While the quality is generally high, some customers have noted recent price increases and a high minimum purchase weight of 250g for the daigaku-imo, which can be a lot for a solo snacker. There are also occasional reports of inconsistency, such as dry or stale pieces, and some have found the service to be brusque or the registers slow during busy times.
Reviewers in 2024–2026 reported paying around ¥950–¥1,000 for a typical 250g portion of candied sweet potato. A single sweet potato cake costs about ¥380–¥400, and a tasting set was noted at ¥1,950. Most feel the taste justifies the price for a premium product, but the minimum portion size makes it less of a casual bargain.
- Location: Find the counter on the B1 floor of the Daimaru Tokyo department store, which is directly connected to Tokyo Station.
- Booking: This is a takeout counter; no booking is needed for a standard purchase. Reservations are listed as available, likely for large or pre-arranged gift orders.
- Payment: Credit cards, electronic money, and QR code payments are all accepted.
- Utensils: Forks are not always included automatically. If you plan to eat your snack on the go, be sure to ask for one at the counter.
- Accessibility: The space in front of the counter is narrow and can become crowded, which may be difficult for those with strollers or wheelchairs.
