Detailed guide to the fourth day of Snow Drop with BLUE title:
In order to get to the fourth day with the blue title, you have to uncover the secrets of the present situation and the secrets in Minoru's past. This may only be achieved by passing through several key-scenes in the story. If one of these scenes is missed, the main mystery of the story will remain uncovered and the normal ending will be triggered.
I will list the necessary scenes in chronological sequence. It is up to the player to find the correct locations, where these events take place.
This is not an event, but a vital choice the player has to make, so this time I will also bluntly say what to do and what I think is the background that makes this choice the only right one. From a roleplaying point of view, the attitude of Minoru towards the others is chosen at this point:
Apologize to Kyoka, even though it might be embarassing!
The story at this point does not change, whatever decision is made at this point. But the chance of getting to a "true" ending with the wrong attitude is zero. If you don't care about the others, it would be unlikely that they would share their secrets later on with you. Even if you watched the necessary scenes, a mistake at this decision would keep you away from "true" endings.
In the morning, you will watch something odd about Shizuka before going to the slopes.
In the evening, you will accidentally peek on Honami, and then a talk with Shizuka about nightskiing. Also, you will find out what happened to Kasumi's husband.
Before going out to the slopes, you have to watch Shizuka in an embarrassing position.
On the slopes, you will have a (literal) collision with Shizuka.
In the evening, you will again be talking alone with Shizuka, hear Kyoka talk in her sleep about events in the past, and at last watch an intimate scene featuring Shizuka and Kasumi.
These are the necessary events to trigger the entrance to the "true" ending. Anyway, it would be a good idea to stay away from Keika as much as possible, because she acts in many cases as a distraction that protects the secrets. It may be (not checked) that the game also closes the way to the blue (true) 4th day, if too many Keika events have been watched, even if all necessary events have been seen.
I have definitely tested that passing these necessary events only and all other places in the schedule with "empty events" (meaning: to meet nobody at all) works in order to reach the "other" 4th day.
Also, there are further decisions to be made on the fourth day and making not the right decisions could lead back to the normal 5th day with the normal ending, so reaching the "true" 4th day is just reaching 3rd base, not a homerun.
Lastly, I have only summarized the events necessary to reach the blue-titled 4th day. There are other events in all 5 days, that have an impact on what "true" ending will be triggered.
Besides the "normal ending" and the "bad endings" (believe me, you will notice, if you reach one of these) there are 4 "good" or "best" endings. The most obvious difference between a "good" and a "best" ending regarding the same girl are the credits at the end of the ending.