Mapping in progress construction from google maps is fun.
First one was Watari Tunnel (渡島トンネル).
Here's Nifuku Tunnel (二股トンネル), Bifuka Tunnel (碧雲トンネル), Notaguchi Tunnel (野田追トンネル) and after Yakumo Tateishi Tunnel (立岩トンネル).
@matrix Why are you interested in this in particular?
@Mr_NutterButter I watched an Abroad In Japan video riding the shinkansen, checked the stops on Google Maps, decided to scroll the entire line and noticed there's construction in progress
Makomanai Tunnel (幌内トンネル), Toyono Tunnel (豊野トンネル) and Kunimatsu Tunnel (国縫トンネル).