Here are the choices you need to make in order to get this achievement :
*** Spoiler - click to reveal ***--The first choice doesn't matter
DAY 1--------------------------------------------------------------------------------------
Reply
Run after him
Do not attempt to take the cutlet
--It doesn't matter if you take the keys or not
Keep silent
DAY 2--------------------------------------------------------------------------------------
Map: Go to infirmary, clubhouse, library & music club
Go get the cards with Slavya
Do not bet with Alisa
--I don't know if you can influence the tournament so...
Map: Go to the Bus Stop if you can
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'd rather help Slavya
Run away
--It seems with the choices made before that you cannot choose anything at the dance party
DAY 4--------------------------------------------------------------------------------------
Map: Go to Olga's house then to the forest
Just asking...
Overdose of stolen candies, right?
Do not ask
Do not give Alisa the activated carbon
--It doesn't matter if you eat the apple or not
Go with Slavya
Keep going right
DAY 5--------------------------------------------------------------------------------------
Map:Go to the infirmary
Go with Slavya
Thanks to the girls' help!
Map: Go to the infirmary, club house and then to the library
Try to snatch the book out of Alisa's hand
Do nothing, just stay seated
Try to find Slavya
DAY 6--------------------------------------------------------------------------------------
For the bad ending:
I was just hungry
We have no reasons to justify ourselves
For the good ending:
I want to get something for Slavya
I have nothing to justify myself for