The Star Brand is a symbol that appears on special individuals in the Conception franchise. In Conception: Please Give Birth to My Child!! and Conception Plus: Maidens of the Twelve Stars, there are 13 different Star Brands, one for each of the 12 astrological zodiac signs and one for Ophiuchus in Plus. Every 120 years when the Star Wards start to weaken, a virgin woman of any age has a chance to have a brand with one of these symbols appear anywhere on their bodies and become a Star Maiden as a result. As long as they have a brand, they won't age until the brand disappears once their service has been fulfilled or for 120 years. When Itsuki arrived on Granvania, he had all 12 Star Brands appear on his body since he was the God's Gift and the "Star Chaos" happened about three months ago. It seems this common for the God's Gifts that are transported from to Sora to Granvania. Mahiru Konatsuki was an exception. Normally, only male God's Gifts are summoned and receive the brand of the ward that is weakened after every 10 years. It was not entirely known why Mahiru was summoned and why she received the Virgo Star Brand, but she has the abilitys similar to others with a Brand and she alone could perform the the Grand sealing Ceremony.
In Conception II: Children of the Seven Stars, on a Disciple between the ages of 16-18. The symbol shows that they contain Star Energy/Star Ether which depends on gender. This power was granted by the Star God in hopes of gifting others to being the savior for the turn of events that have begun. If someone has a Star Brand, it will appear on the back of their hand.
Those who bear the Star Brand are then sent to the Aterra Academy to be educated to use the Star Energy they were given. In the game, the brand usually displays a magenta color. However, heroines are given a different brand color.