If I had to choose a favorite from my recent trip, Ramenya Tenkin would be very near the top. A two-day process of boiling pork bones (豚骨) and chicken bones (鶏がら) defines this top-notch soup. Add some thick shoyu that's derived from the chashu making process and viola!...The signature Asahikawa-style Shoyu Ramen is born. Almost everyone I talked to said Tenkin was their favorite. And that's some high praise in a city filled with great ramen shops on almost every corner. You get a free bowl of rice during lunch, but if you want to avoid the crowds I recommend you go around 2 or 3.
From Asahikawa Station head right away from the main shopping street and take a left on the next big street. It's the street where you see all the taxi drivers entering their parking lot. Head north away from the station for seven blocks then make a right. Ramenya Tenkin will be on your left. Grab a seat and place an order with the waitress. They are open from 11am-9pm and closed on holidays.
Other sites that mention Ramenya Tenkin: