Be careful as there's gonna be spoilers ahead.
Endings in Angels with Scaly Wings always occur during Chapter 5 of a playthrough. There's two endings for each main characters, one good and one bad. There's also three other endings, a neutral ending, an evil ending and a true ending, totaling up to 13 different endings in the game.
For each of the character's individual endings, not only you must complete all four of their dates successfully without their Status in either Bad or Abandoned, but you also must keep them alive before going to the fireworks with them.
Remy's Endings
Remy's Bad Ending
Don't ask Remy about children during his third date. (Unlocks the achievement Alone and Remy's shadow at the Main Menu.)
Remy's Good Ending
Look through Remy's pictures during his second date, follow Vara at the store during the third investigation and ask Remy about children during his third date. (Unlocks the achievement Casualties of War, Remy at the Main Menu and his artwork at the Gallery).
Anna's Endings
Anna's Bad Ending
Don't tell Anna that she has cancer during her fourth date. (Unlocks the achievement Sacrifice and Anna's shadow at the Main Menu.)
Anna's Good Ending
Take the envelop at Anna's lab during her second date and tell her that she has cancer during her fourth date. (Unlocks the achievement Tragic Hero, Anna at the Main Menu and her artwork at the Gallery.)
Lorem's Endings
Lorem's Bad Ending
Don't take the assembled Ixomen Sphere to Lorem at the fireworks. (Unlocks the achievement Remember and Lorem's shadow at the Main Menu.)
Lorem's Good Ending
Search the pavilion three times for the Ixomen Sphere at Tetsu Park during the second investigation, search the trash can for the Ixomen Base at the Police Archives during the third investigation and take the assembled Ixomen Sphere to Lorem at the fireworks. (Unlocks the achievement The Plan, Lorem at the Main Menu and his artwork at the Gallery.)
Bryce's Endings
Bryce's Bad Ending
Don't give Maverick your blood during the fourth investigation. (Unlocks the achievement Catastrophy and Bryce's shadow at the Main Menu.)
Bryce's Good Ending
Take a blood test with Anna during Chapter 1 and give Maverick your blood during the fourth investigation. (Unlocks the achievement Murderer. Bryce and the Main Menu and his artwork at the Gallery.)
Adine's Endings
Adine's Bad Ending
Don't give Adine the facility map during her third date. (Unlocks the achievement Getaway and Adine's shadow at the Main Menu.)
Adine's Good Ending
Study the blueprint and take the facility map at the Police Archives during the third investigation and give Adine the map during her third date. (Unlocks the achievement Decisions, Adine at the Main Menu and her artwork at the Gallery.)
Other Endings
Neutral Ending
Go to the fireworks alone. (Unlocks the achievement Detonation and changes the Main Menu's time of day to Dawn.)
Evil Ending
Make jerk choices, perform poorly during all investigations, make everyone's Status to Bad and go to the fireworks alone. (Unlocks the achievement Betrayal and unlocks Reza's artwork at the Gallery.)
True Ending
After receiving the Good endings with each of the main characters, go to the fireworks with everyone. (Unlocks the achievement Hope and Izumi's artwork at the Gallery as well as changing the Main Menu's time of day to daytime.)