You have Died and have been reincarnated into the world of Mushoku Tensei a world with mages and swordsmen you will start the story age and will progressivley age within the story. once you turn fifteen{the adult age in this world} the  Metastasis Event will happen. Will you lead a normal life become an adventure or aim for the goal of become one of the seven great powers? the seven great powers are the seven strongest people in the world and are hard to find to become one you haveto kill one 

Become a mage or a swordsman or maybe both

Make it to the championship and beat the generation of miracles

Make it to the championship

Flowey used to be Asriel dremurr until he was killed and came back as a flower toriel and asgore are his parents but they don't know that he is their son and doesn't want them to know so he refuses to see them.  he is the first person you see as soon as you fall down mt ebott.

He is kind and resonable he will kill if needed to

He'll only become a little after your long and difficult battle with him and after you spare him. He is sans younger brother but is more serious then him. If you dont fight him he forces you to fight him.

Rude,serious and confident and he swears a lot. 

to defeat froggit you have to kill it or you have to compliment it.  it attacks you by jumping on you and throwing flies at you. froggit only appears in the  ruins and core. froggit can't talk.

it attacks you

Make it to the championship and beat the generation of miracles.

Adventure Time is an American fantasy animated television series created by Pendleton Ward for Cartoon Network.  set in the aftermath of the mushroom war, of which a magical world emerged from the ruins. You are in the land of ooo which is divided into many different kingdoms, of which the most prominent are the Ice Kingdom, Candy Kingdom, Wildberry Kingdom, Lumpy Space, Fire Kingdom, and Cloud Kingdom.

You are in the world of adventure time

This narrator will give you the underfell story line the  au of undertale.  Underfell follows the story of Frisk and Flowey as they traverse through a world of monsters who believe that the meaning of the world is to "killed or be killed" thanks to Asgore. The underfell is your choice maker. whenever you enter battle it gives you theses choices fight act item and mercy. the mercy button wont  work all the time your soul is determination. every character is from underfell no matter the name.

your are in the Undertale au: Underfell

he will only appear after you meet papyrus(underfell) One you reach the judgment hall  he will judge you if you havent killed anyone he'll fight you until you choosefight and will allow you to kill him. If you kill everybody hell fight you to the death and will be extremley hard to beat and he wont allow you to kill him. if you kill a few people hell let you pass and wont fight you  He is crude, mean  he hates papyrus but calls him boss