A possible concise summary is:
Toya, a teenager who was killed by God's lightning bolts, is sent to another world with a smartphone and magic abilities. He meets twin sisters Elze and Linze, who teach him magic and join his party. He also meets Yae, a samurai girl who becomes his friend. He saves a noble girl named Sushi from lizard men and is invited to her father's mansion. There, he heals Sushi's blind sister Ellen and is offered Sushi as a child bride. He declines and escapes with his friends. He is happy with his new life.
Here are the key facts from the text:
1. Toya Mochizuki arrives in heaven.
2. God tells Toya that he was supposed to live for another 70 years, but God accidentally killed him with one to five lightning bolts while Toya was on the toilet.
3. Toya is not sent back to his world, but is offered a chance to go to another world with magic and adventure.
4. Toya chooses to go to this new world and is given a new smartphone, an iPhone 20, which can pipe music directly into his brain.
5. Toya meets Elze and Linze, twin sisters who are on a quest, and joins them on their journey.
6. Toya learns magic from Linze and becomes very powerful.
7. Toya and the sisters go on a quest to save Sushi, the daughter of Duke Ortlinde.
8. Toya heals Sushi's butler, who was injured by a piece of lizard that was blown up.
9. Toya and the sisters meet Duke Ortlinde, who is a cruel and sinister character.
10. Toya heals Duke Ortlinde's daughter, Ellen, who was blind and weak.
11. Duke Ortlinde rewards Toya with a platinum sphere and offers him a child bride, which Toya declines.
12. Toya and the sisters escape from Duke Ortlinde's castle while he is distracted by singing.