Here is the full list of all 18 Sankaku Renai: Love Triangle Trouble achievements.
Cleared the Akane route.
Got a glimpse into Akane's mind.
Cleared the Nanaru route.
Hit the mark.
Cleared the Suzu route.
Served some yakisoba.
Cleared the Cara route.
Resisted the urges.
Cleared the Maho route.
Had some Ice Cream with Maho (and an extra).
Cleared the Shiina route.
Witness the Cook-off.
Lit up some fireworks with the gang.
Cleared the common route.
Discovered Nanaru's dirty secret.
Witness Maho comboing everyone else.
Witnessed a tragic event.
Confirmed Shiina's dedication.