Fosterson is a relationship between Thor and Jane from the Thor fandom.
They first met, when Dr. Donald Blake hired Jane Foster to assist him in his private medical practice. Although, Dr. Donald Blake was actually the human identity used for many years by the Asgardian god Thor. Blake fell deeply in love with Foster, who was unaware of his dual-identity. Jane was infatuated with Thor, whom she had not yet met in his godly identity, but took a protective attitude toward him, worrying about his health and frailty.
However, Foster was strongly attracted to Blake, who feared that Foster did not love him, but merely pitied him. Thor's foster brother Loki, knowing his feelings toward Foster, endangered her life in order to attack him several times. Afterward, Blake decided to reveal his dual-identity to Foster, but his father, Odin, monarch of Asgard, appeared to him and forbade him to reveal this secret to any mortal. Even though Odin tried for a long time to quash the romance between the two, he ordered her life to be saved when she lay dying after an explosion caused by a battle between Thor and Mister Hyde and Cobra.
Foster truly loved Blake, and one day she told him angrily that she would not wait forever for him to declare his love to her. Thor intended to marry Foster, but then Odin forbade him to marry her on the grounds that she was a mortal, not a goddess. Thor later asked Odin to reconsider the issue, and Odin relented, saying that Thor could marry her if she proved herself worthy.
The superhuman criminal Mister Hyde, seeking vengeance against Blake, captured both him and Foster, and made Blake prisoner in a room with a bomb. Blake escaped and, as Thor, battled Hyde; but Foster, fearing that only Hyde could save Blake's life by deactivating the bomb, helped Hyde to escape. Outraged by this seeming betrayal against his son, Odin rejected Thor's petition to marry Foster. Foster was menaced repeatedly by enemies of Thor who either knew he was Blake, or knew there was some connection between Thor and Blake. Such assailants included Hyde and his partner, the Cobra; his bitter foster-brother Loki; and the Enchantress and her partner, the original Executioner; as well as the journalist Harris Hobbs. As Thor rescued her from these many perils over time, Foster fell deeply in love with him.
Finally, Thor defied Odin and revealed his dual-identity to Foster. Foster left America and took a position with a man who proved to be the High Evolutionary. Thor followed her to the High Evolutionary's citadel at Wundagore Mountain, where they were reunited. Again petitioning Odin to let him marry Foster, Thor brought her to Asgard itself, a place forbidden to mortals.
Odin agreed to let them marry if Foster proved herself capable of functioning as an Asgardian goddess. Odin then physically transformed Foster into an Asgardian, granting her superhuman powers. As Odin must have expected, Foster was confused and bewildered by her new abilities and by Asgard itself. Declaring that Foster had failed his test, Odin turned her back into a mortal woman, sent her back to Earth, and removed her memories of her experiences with Thor. Odin sent Foster to work for the physician Dr. Keith Kincaid, and the two soon fell in love with each other.
As for Thor, Odin saw to it that he was reunited the Asgardian goddess Sif, whom he had loved in the past, and their romance was quickly rekindled. Years later, Foster fell ill and, lying close to death, called out to Thor in her delirium. Sif stole the enchanted Runestaff of Kamo Tharnn, the Elder of the Universe known as the Possessor, and used it to infuse her own life-force into Foster, thereby saving her life. Sif vanished, and Foster recovered, also regaining full possession of her lost memories of Thor. The love between Thor and Foster revived, but soon she was captured by trolls under the leadership of Thor's enemy Ulik. To Thor's surprise, Foster succeeded in capturing the troll king Geirrodur with his own spear; Thor himself defeated Ulik.
Thereafter, Foster insisted on accompanying Thor on various exploits, traveling with him to the dimension of the god of Heliopolis, to the alternate future Earth ruled by the Tomorrow Man, and to the war-torn nation of Costa Verde. (Thor attributed Foster's new liking for adventure and fighting spirit to the presence of Sif's spirit within her, although it is possible that Foster's personality had simply evolved this way on its own.) After some time, Foster finally insisted on accompanying Thor to Asgard. There, the Asgardian Grand Vizier presented her with Sif's sword and when she struck it against a wall, she was seemingly transformed into Sif. The Vizier theorized that Foster and Sif had become one being, and that Sif would be dominant in Asgard, and Foster on Earth. Yet when Sif returned to Earth many months later, she did not transform into Foster, to Thor's puzzlement.
Jane first met Thor when she was traveling in a van with her colleague Erik Selvig, and her assistant Darcy, when the mysterious weather event subject of Foster's research unexpectedly resulted in a powerful vortex before them. As they struggled with the zero-visibility conditions, the van collided with a man who had stumbled out of the dust into their path. The man, who only announced himself as Thor, was injured again when Lewis tazered him, prompting them to take him to hospital. These events transpired in Puente Antiguo, New Mexico.