https://www.cmoa.jp/title/312003/

Tsubaki is in the midst of the happiness of her life when she gets married to her childhood friend. However, something suspicious suddenly appeared at the wedding... and when she woke up, she was a baby! It seems that she has been reborn in another world as Millie, the youngest daughter of a duke, with memories of her previous life. She recalls the cause of Tsubaki's death, but has no idea what it was. She is determined to enjoy her new life to the fullest, but to her surprise, she has six unique and beautiful older brothers...! Millie is doted upon by her gorgeous family and her days seem to be peaceful, but an unexpectedly hard fate awaits her...? Source: MU

A young man who should have died in an accident is reborn as Arte, the second son of a powerful marquis family in a world of swords and magic. Surrounded by a loving family, he enjoys a smooth and prosperous life. However, during the selection ceremony to receive magical abilities, he is granted a mysterious innate magic called "Light." While others dismiss it as a "failed" magic, Arte’s past life memories return, revealing the true nature of his magic…!? Using his past life's knowledge, he aims to transform this "failed" magic into the "strongest" magic…!? The strongest and freest adventure of a man known as "Flash" begins now—!