More information on Ichigo can be found on the Heroes Wiki.
BiographyIchigo and Orihime are in the same year at high school. They're mutual friends of Tatsuki Arisawa. It's later mentioned that Ichigo and Orihime met very tragically: she dragged her older brother Sora to the clinic owned by Ichigo's father Dr. Isshin Kurosaki after he was severely injured in a accident, and he died in front of Orihime and the Kurosaki family.
Sometime after Ichigo gained the powers of a Soul Reaper (a spiritual cleanser and warrior), Orihime was attacked by a Hollow (a malevolent masked spirit). Ichigo and Rukia (the Soul Reaper who gave him his powers) arrived in time to stop the Hollow, revealing it to be the corrupted soul of Orihime's dead brother. Ichigo and Rukia allowed Orihime and Sora to make their peace before he was purified and sent to the afterlife.
Sometime later, a swarm of Hollows invaded their town, leaving Ichigo in a difficult place as all of his friends and loved ones were at risk of being killed by them. When Orihime and Tatsuki were attacked by a Hollow, Orihime revealed her own latent spiritual powers and defeated it. She then decides to join Ichigo on his adventures.
When the Arrancar (unmasked Hollows) invade, Orihime is badly beaten, leaving Ichigo feeling guilty about not protecting her. Both resolve to improve their skills in preparation for the next assault, and in the meantime Rukia got Ichigo to specifically protect Orihime as compensation for not having been able to be there for her. An Arrancar named Ulquiorra corners Orihime and threatens to kill her friends if she doesn't agree to join their side. Ulquiorra gives Orihime one night to say her farewells to the person she cares most about. Orihime sneaks into Ichigo's room while he's sleeping and confesses her love for him. She also tried kissing him in his sleep, but backed away at the last second out of shyness.When Ichigo finds out that Orihime was abducted by the Arrancar, he gathers his closest allies (Rukia, her best friend Renji, Ichigo's best friend Chad and his rival Ishida) and launches an attack on their fortress. He gets to Orihime, only for her to be pulled out of his reach once again. Ichigo finally catches Orihime being guarded by Ulquiorra and the two duel for her freedom. Ulquiorra overpowers and kills Ichigo, causing Orihime to panic. The last thing Ichigo hears is Orihime crying his name, which causes his own power, revive him, corrupt and turn him into his full Hollow form. Hollow-Ichigo then brutally beats Ulquiorra down, the only damage he took was to his mask, which was enough to cause Ichigo to change back. Ulquiorra then dies from his injuries.
A year later, Orihime is attacked by a new enemy known as Tsukishima. He cuts Orihime, but doesn't kill her for some reason. When Ichigo finds out, Orihime tells him that Tsukishima is an old friend of hers without realizing it. It is later revealed that Tsukishima has the ability to insert his prescence into someone's past and used this ability to make Orihime think he was someone she could trust. After using the same ability on everyone Ichigo knew, Ichigo decides to kill Tsukishima, only to be stopped by Orihime. When reinforcements arrive and aid Ichigo, Orihime begins to question Tsukishima's presence in her memories. The fact that none of it adds up in her mind causes Orihime to pass out, though she later recovers after Tsukishima is killed in battle.
Later in the series, Orihime and Ichigo are still close friends and teammates. She, alongside their other friends, follow him into Hueco Mundo and then Soul Society when Yhwach and the Vandenreich attack both world. Near at the end, Ichigo personally chooses Orihime to help him in the final battle against Yhwach, and while Yhwach defeats them both they do put a good show together against him.
10 years later, Ichigo and Orihime are happily married with a son named Kazui.
Relationship with OrihimeFor the most part, Ichigo is fairly indifferent to the idea of love. He cares about Orihime, though some people say that this is mainly because of his innate urge to protect people. Orihime suspects that Ichigo has never seen her as more than a friend, however she believes that it's good enough to be by his side to thank him for everything he's done for her sake. Though, like any normal girl, she often fantasizes about Ichigo. There have been instances where Orihime has shown a 6th sense regarding Ichigo, such as the time his body was possessed by a rogue soul, implying that her attraction to him might be on a deeper level than previously thought. Another time was when Orihime was affected by Tsukishima's powers, and her feelings and emotions ended up taking over his power to brainwash her resulting to her cry in tears.
As it turns out, Ichigo has always had a soft spot for Orihime and is extremely dedicated to protecting her. Rukia, his and Orihime's close friend, comes up with the idea of having Ichigo formally promising to protect Orihime after she's severely wounded. Several rivals also point out Ichigo's pretectiveness of Orihime, directly using her as leverage against him to goad Ichigo into fighting harder. This reaches its critical height when Ulquiorra fatally injures Ichigo in front of a mentally-broken Orihime... and he was revived from the dead because of Orihime crying for his help, focusing completely and wildly on protecting her.