If you want to master the senmai, go to Jonetsu Horumon! @ Shinjuku Omoide Yokocyo Sakaba Jonestu Horumon
The senmai is the third stomach of the cow, and Jonetsu Horumon has two types of senmai on the menu.
One is the ‘Yaki-Senmai’, which is grilled on a shichirin (a charcoal grill). The other is the snack ‘Koku Shiro Senmai’.
These two types of senmai are completely different in appearance.
The Yaki Senmai is dark and rough, while the Goku Shiro Senmai is white, firm and shiny.
The sauce is also different, so you can enjoy completely different tastes and textures.