You need to have at least one good ending done before attempting to do this
Here are the choices you need to make in order to get this achievement :
*** Spoiler - click to reveal ***No I'll stay here
DAY 1--------------------------------------------------------------------------------------
Do not reply
Run after him
Do not attempt to take the cutlet
Take the keys
Keep silent
DAY 2--------------------------------------------------------------------------------------
Map: Go to music club, infirmary, clubhouse, library
Go alone
Do not bet with Alisa
--I don't know if you can influence the tournament so...
Map: Go to Genda Square or to the beach
DAY 3--------------------------------------------------------------------------------------
Fine, wait a minute
You know, Olga asked me to help her tonight...
Who cares? I'd better keep looking for answers
I think I'd rather assist the guys with their giant robot engineering
--The next choice doesn't matter
DAY 4--------------------------------------------------------------------------------------
Map: Go to the Bus Stop
Go with Miku
Map: Go to the Boat House
Just asking...
Overdose of stolen candies, right?
Ask about the bundle
Do not give Alisa the activated carbon
Do not eat the apple
Go alone