Mammon

• He panics when you tell him your birthday already passed. How could Mammon the Great forget the birthday of his favorite human? He hugs you close, apologizes, and promises to make it up to you.
• Since he isn’t sure what to do, Mammon asks what you want to do. He says he will do whatever you want for the entire day, no matter how crazy your request is.
• But then he adds, he will give you two choices since you’re his favorite human: either you can get one item using Goldie, or he will be yours for the entire day, as in you can do whatever with him or get him to do whatever you want.
• Before you answer, Mammon adds while blushing, “Don’t get used to this. I won’t do this ever again…this is a one-time thing only.”

• Levi feels horrible for forgetting the birthday of his special friend. He mentally curses himself for being a bad friend, and even if you tell him it’s okay, Levi won’t forgive himself easily.
• He spends the entire night making a short birthday game but isn’t confident enough to show it to you.
• The next day, he asks if you want to go out with him, even though he doesn’t want to leave the comforts of his room. If you plan to go out, Levi will do his best to deal with the crowds of people, but if you choose to stay at home, he will spend the entire day watching your favorite movies/shows/animes.
• Towards the end of the day, Mammon messages you, asking if Levi showed you the game he spent the night making for you.
• When you ask him to see the game, Levi gives you access to it but hides behind you, thinking you won’t like it. The game is simple with you/MC collecting gifts in a world that looks like Devildom, and at the end, a message appears: “For my favorite person. Thank you for playing! I am sorry for missing your birthday. Hope you’re not upset.”

• Satan apologizes and asks if you would give him a chance to make it up to you. Even if you tell him he doesn’t have to, Satan refuses to let you go until you say yes.
• First, he takes you out to his favorite cat cafe, then he takes you shopping, treating you to everything you like, and finally, brings you to your favorite restaurant.
• At the end of the day, he leads you to the most beautiful place overlooking Devildom and hands you a gift bag. Inside is a pair of cat earrings. Satan says he will not forget your birthday again, and if he does, you can give him any punishment you want.

• Belphie feels bad for missing your special day but also thinks trying to make it up will take too much effort. If only you would agree to take a bday nap with him.
• He ends up asking his brothers for help and arranges a party with gifts, food, and a performance by Asmo/Mammon. There is also a karaoke machine, in case you want to sing or hear someone else sing. For the most part, Belphie watches you while trying not to fall asleep.
• His present to you is a nice fluffy blanket which you can use to take naps, hopefully with him.
• Even though Belphie gave up on his sleep to attend the party, he’s glad he stayed up. Your smile made his efforts worthwhile.

• Beel pouts and says sorry for forgetting your birthday. He offers to take you to your favorite place and treat you to all the food you want.
• He can’t sleep that night and thinks of a way to make it up to you. The next day, he takes you out on an “all you can eat” date before taking you to a carnival.
• There, he rides as many rides you want and treats you to any food you want to try.
• In the evening, he asks if you had fun. Beel then hands you a giant orange teddy bear he won at one of the carnival games. He tells you to hug the bear if you ever miss him when he’s not around. Beel even named the teddy bear Beel 2.0.  

• He gasps and apologizes before canceling all his plans for the day. Asmo wants to spend the entire day and night (if you permit him) pampering you.
• His plan starts with taking you to the spa, followed by the salon for a makeover. Then he takes you shopping for new clothes and your bday gift, and finally, Asmo brings you to your favorite restaurant.
• If you permit him to pamper you at night, then he will take a long bath with you, give you a massage, and have a sleepover with movies, gossip, and whatever else you like.
• His special gift to you is an annual spa pass to use when the brothers stress you out too much.

• Lucifer feels another mountain of stress piling on his head. He is supposed to make you feel at home, yet he managed to forget your birthday despite reading the date on your transfer form. 
• The Avatar of Pride doesn’t apologize; instead, he quickly assembles his brothers and plans a party with them. Lucifer gives them one warning: everything HAS to be perfect, and if anyone messes anything up, he will severely punish them. 
• While his brothers are preparing for the party, he invites you out to go shopping. Every time you stare at an item for more than 10 seconds, he secretly buys it. 
• By the time you return to the House of Lamentation, everything is in place. You party with the brothers for hours, and when you finally go to your room, there is a pile of gifts waiting for you. On top of the mountain of boxes is a note: “Did you enjoy the party? I shall not forget your birthday again. Thank you for supporting all of us and putting up with our family drama. Now, off to bed. You still have to attend classes tomorrow.” 

• Diavolo is devastated and can’t believe he missed your birthday. He’s upset with himself for not asking you sooner and continuously apologizes verbally and through text messages.
• The prince plans a party for you and asks Barbatos/the demon brothers to set everything up for the best birthday party.
• His gift for you is an “Eternal Rose”, a rose that will never wither. As he hands you the flower, he whispers, “The day this rose withers is the day I will stop admiring you.” 
• This time he may have missed your birthday, but next year, he plans to decorate Devildom for your special day. Be prepared to party the entire day.

Simeon

• Simeon is upset at himself for not finding out sooner. He apologizes and promises to make it up to you even if you tell him, it’s okay. 
• He prefers to host a small party with only the members of Purgatory Hall. Luke prepares the food, Solomon puts up the decorations, and Simeon makes a quick gift run. 
• His gift to you is a bouquet of white flowers with a simple but beautiful pearl necklace. 
• Towards the end of the party, the angel invites you out on the balcony. While staring at the sky, he thanks you for always staying by his side. Simeon promises to be there for you for the rest of your life – as a lover, life partner, or guardian angel. He leaves the choice up to you.