If you use Tempura Pass, you can get a piece of tempura for free. However, you have to buy one udon.
The pass costs 300 yen (includes tax) and is available from April 1 through 7 May 2017 at Hanamaru Udon はなまるうどん restaurants in Japan.
New! September 15 – October 23, 2017

Tempura Pass is called Tempura Teikiken 天ぷら定期券 in Japanese.
The pass is now on sale (from March 24 September 1, 2017), but the quantities are limited. First come, first served.
You can use the pass as many times as you want from April 1 through May 7, 2017 September 15 through October 23, 2017.
The pass is sold at the cash desk in the restaurant.
(Update 9 April : The pass is already sold out at some restaurants.)
はしご定期券
Hanamaru Udon はなまるうどん restaurants offer many kinds of Udon. You have to choose one udon or one set meal (includes udon), if you use the pass.
They offer several kinds of tempura such as shrimp, mixed vegetables, fish sausage, chicken and others. A piece of tempura costs 100 yen to more.
Udon うどん
This is the lowest price udon Kake-shou かけ小 (small size kake-udon) for 130 yen. This udon is also accepted to use the pass. Such a cost effective!

* The list prices are sometimes a little bit different at respective shops.

Hanamaru Udon はなまるうどん is chain restaurant and there are so many restaurants in Japan.
Around central Tokyo :
Google maps Please find the restaurants which are named Hanamaru Udon はなまるうどん on the map.

About the pass (in Japanese)
https://www.hanamaruudon.com/tempurapass2017autumn/

Official website
http://www.hanamaruudon.com

Picture menu
http://www.hanamaruudon.com/menu/

* You can use the pass for these food items below.
Mixed vegetables tempura かき揚げ Kakiage
Mixed vegetables tempura 140 yen (かき揚げ Kakiage )

Prawn tempura えび天 Ebiten
Prawn tempura 140 yen (えび天 Ebiten)

Note
The pass accepts customers in group such as your family or friends. You can present the coupon and pay for all. Individual payment for a single coupon would not be accepted.Calamari tempura いか天 Ikaten

Calamari tempura 110 yen (いか天 Ikaten)
Calamari tempura いか天 Ikaten

Chicken tempura とり天 Toriten
Chicken tempura 140 yen (とり天 Toriten)
Chicken tempura とり天 Toriten
Sauce and soy sauce are available.

Fried mashed potato コロッケ Korokke
Fried mashed potato 120 yen (コロッケ Korokke)
Fried mashed potato コロッケ Korokke
Hokkaido 北海道 Japan grown potato

Fried chicken 鶏の唐揚げ Tori-no-karaage
Fried chicken 100 yen (鶏の唐揚げ Tori-no-karaage)

Nori flavor chikuwa tempura, Fish paste sausage ちくわ磯辺揚げ
Nori flavor chikuwa tempura 110 yen (ちくわ磯辺揚げ Chikuwa-isobeage)
* Chikuwa is a kind of fish paste sausage.

Sweetpotato tempura さつまいも天
Sweetpotato tempura 110 yen (さつまいも天 Satsumaimo-ten)

My Best
Squid arms tempura げそ天
Squid arms tempura 160 yen (げそ天 Geso-ten)
Squid arms tempura げそ天
Squid arms tempura 160 yen (げそ天 Geso-ten)
Squid arms tempura げそ天
I often put sauce on it.

Note
The shop also offers other kinds of tempura and food items, but they are not included in the pass promotion.

Information
The company of this udon chain also has beef bowl chain YOSHINOYA 吉野家.
At this beef bowl chain you can get a 80-yen discount for the following set of items when you show the pass:
– Bowls 丼 (Beef bowls, Pork bowls, etc.)
– Set meals 定食
– Dish 皿 (Beef dish 牛皿, etc)
– Curry カレー
Beef bowl 牛丼
Beef bowl 380 yen (牛丼 Gyuudon)
Beef bowl 牛丼
Around central Tokyo :

Google maps Please find the restaurants which are named Yoshinoya 吉野家 on the map.

Website
https://www.yoshinoya.com/en/

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