This achievement is unlocked by completing the game with Kisaki's ending. (Kisaki route complete)
To get to this ending, make the following choices. See the end of the list for details of the notation used.
(10/21) 1 / 2 [7:9]
(10/21) 2 / 2 [11:12]
(10/21) 1 / 2 [12:12]
(10/22) 2 / 2 [4:4]
(10/23) 1 / 2 [9:11]
(10/23) 2 / 2 [4:4]
(10/24) 1 / 2 [6:7]
(10/26) 2 / 2 [13:14]
(10/27) 1 / 2 [5:5]
(10/29) 1 / 2 [5:7]
(10/29) 1 / 3 [8:7:8]
(10/31) 2 / 2 [4:4]
(11/3) 2 / 4 [4:2:4:4]
(11/3) 2 / 4 [4:2:4:4]
(11/5) 1 / 2 [7:9]
(11/5) 1 / 2 [11:12]
(11/9) 1 / 2 [10:12]
(11/11) 1 / 2 [7:9]
(11/12) 1 / 2 [11:11]
(11/12) 1 / 2 [12:12]
(11/13) 1 / 2 [10:13]
(11/14) 1 / 2 [12:10]
(11/14) 2 / 2 [7:9]
(11/15) 2 / 2 [8:5]
(11/16) 2 / 2 [8:10]
(11/21) 2 / 2 [10:9]
(11/22) 1 / 2 [9:11]
(11/22) 1 / 2 [8:4] (I recommend making a save before selecting this choice.)
(11/26) 1 / 2 [11:12]
After clearing the game, select "YES".
Each choice has three parts of information.
(10/21) : The in-game date when this choice appears. While playing, pressing Y button will show this date.
1 / 2: Right number shows the total number of choices available. Left number shows the number of the choice you have to select (counted from the top). In this example, you have to select the first (top) choice from two choices.
[7:9]: Shows the number of characters each choice has. This is a rather supplementary info to help you when you feel losing your way. Usually, you don't need to count this every time you make a choice. In this example, this part shows that the first choice has 7 (Japanese) characters, and the second choice has 9 characters.