Walkthrough by BabaJeanmel
This guide only covers the requirements to unlock all H-scenes, and consequently all endings.
CHAPTER 1
07/08, between 12.00 and 13.59, school backyard (裏庭). Watch the scene involving Mikami.
07/08, between 13.00 and 18.59, Inariyama Park (稲荷山公園). Talk to Chiaki. Return at the same spot to trigger 4 scenes with her. Then, go to Blanche's Department Store (ブランシェ). Choose the top option to go shop with Chiaki, then the top option again to buy her a present.
07/08, between 19.00 and 23.00, Akira's house (洸の家). Talk to Natsune and choose the top option. You'll see an H-scene.
07/09, between 9.00 and 16.59, Blanche's Department Store (ブランシェ). See the scene involving Mikami, then follow her to Cosmic City (コズミックシティ). Choose the top option.
07/10, between 18.30 and 19.59, Cosmic City (コズミックシティ). Talk to Mikami and choose the top option to see the H-scene.
CHAPTER 2
07/22, between 9.00 and 16.59, Inariyama Park (稲荷山公園). Talk to Chiaki. Return at the same spot to trigger 4 scenes with her.
07/22, between 19.30 and 22.59, Inariyama Park (稲荷山公園). Talk to Chiaki and watch the H-scene.
There's a bonus H-scene that triggers automatically at the chapter's end, involving Nogami Sensei.
CHAPTER 3
09/03, 14.00. You'll automatically see a scene with Yayoi at Hikawa Shrine (氷川神社)
09/03, 21.00, Akira's house (洸の家). Talk to Yayoi and choose the top answer. Watch the H-scene.
CHAPTER 4
12/23, between 13.00 and 13.59 (immediately after the start of the chapter), school Rooftop (屋上). Talk to Reiko and choose the top answer.
12/23, after 21.00. You'll automatically go back to Akira's House (洸の家) and watch a H-scene involving Shihori.
12/24, between 8.00 and 10.59, Reiko's house (玲子の家). Talk to Reiko.
12/24, after 16.00. Go to Cosmic City (コズミックシティ) until you trigger Reiko's H-scene.
12/25, between 9.00 and 13.59, Cosmic City (コズミックシティ). Talk to Yuka.
12/25, between 10.00 and 11.59, Omiya Station (大宮駅). Talk to Mio and choose the top answer. Watch the H-scene.
CHAPTER 5
01/31, between 16.00 and 16.59. Go to Washinouha Academy (鷲ノ羽学園) then to the library (図書室). Watch the last H-scene, involving Yuka.
After the last mission, you'll have the choice to tell your feelings to any of the main girls. You can save at that precise point to watch different endings. If you unlocked the girls' H-scene, she'll accept you and you'll see a last H-CG in a whooping 640x800 resolution. If you hadn't met the requirements, she'll reject you.