Insanely amazing Hototogisu changes gears on Thursdays and becomes Ura-Hototogisu. Hidden-Hototogisu. Niboshi heavy soup one day a week.
They also have a limited to 10-a-day Taiwan-niboshi ramen. Spicy nira and an intesne ground pork mix.
I still prefer their normal menu on Thursdays, but go for this one if you have already been and are looking to spice things up.
Make sure you get there about ten minutes before they open, or be subject to a long line.
Another review I did a while back is here.
Tokyo, Shibuya-ku, Hatagaya 2-47-12
Closest station: Hatagaya
Open 11:30-15:00 on Thursdays