it’s either this or the highway (busy and also extremely boring) here... roadbikeable gravel, with the old asphalt still remaining in a few places (and proper asphalt in Kaipiainen village), no traffic
in the west you have to ride on the highway for a little while or take a detour via Mankintie to the north or Metsontie to the south (this road continues a bit further as well but there is no further rideable connection to the highway itself) before the bike path starts, in the east you have to switch to south of the tracks, then back and to the highway between Kaitjärvi and Somerharju and then again to the old road south of the tracks, from Taavetti (Luumäki) on there is a parallel road (with a bike path in many places) to Lappeenranta