One possible plot could involve Ichigo's spiritual energy causing a ruckus in the DxD world. His power might be misinterpreted, and he has to prove that he's not a threat. At the same time, he could learn some unique abilities from the DxD characters, and they from him. For example, the devils in DxD might be interested in Ichigo's zanpakuto and its powers, while Ichigo could gain some knowledge about magic from them.
Ichigo and Issei would be really interesting. Ichigo, with his calm and collected nature most of the time, compared to Issei's more pervy and hot - headed ways. Their different personalities could lead to some really funny and intense interactions, especially when it comes to fighting side by side or arguing about battle strategies.
One possibility could be that Ichigo's unique powers as a Soul Reaper and his transcendental forms could create an interesting dynamic in the DxD universe. Maybe his Hollow powers would be seen as a new type of 'evil' power there, and the devils would either try to recruit him or fight him. Also, his Bankai and its evolutions could make him a formidable opponent against the various factions in DxD.
One interesting character to crossover with Ichigo is Light Yagami from Death Note. The clash between Ichigo, who is a protector, and Light, who is a morally ambiguous character with the power to kill, would be very engaging. Saitama from One - Punch Man could also be a great choice. Saitama's overpowered nature and Ichigo's journey to become stronger would make for an interesting story. And what about Alucard from Hellsing? His vampire powers and Ichigo's powers related to the afterlife would create a really dark and exciting crossover.
Aizen Sousuke would be an interesting crossover character. Since he's so powerful and manipulative in the Bleach universe, seeing him in a different setting with Ichigo could create some really complex and intense storylines. They could be forced to work together against an even greater evil in a crossover universe.
The story could then develop as Ichigo tries to find a way back home. Along the way, he gets caught up in the politics and battles of the DxD world. He might meet Issei and initially be at odds with him because of their different outlooks on power and combat. But as they face common enemies, they start to work together. Ichigo could also have run - ins with powerful devils like Sirzechs Lucifer, who might be intrigued by his power and want to either recruit him or eliminate him as a potential threat.
One great 'Bleach Ichigo Transcendent Crossover Fanfiction' is 'Ichigo in the World of Naruto'. It shows Ichigo's powers in a completely different ninja - filled world. His reiatsu stands out among the chakra - using ninjas. It's an exciting read as he has to adapt to new rules and also face off against powerful foes in the Naruto universe.
Well, it could be about Ichigo having some super - transcendent powers that he has to hide in the High School DxD world. Maybe he's a new student there and his powers start to disrupt the normal balance of the supernatural elements in the school.
Another aspect could be Ichigo's internal struggle in this new universe. He's used to the world of Hollows, Soul Reapers, and Quincy in Bleach. But in DxD, there are new moral and power dynamics. His sense of justice might be put to the test as he encounters situations that are different from what he's faced before. He might have to decide whether to interfere in the power struggles between the three main factions - devils, angels, and fallen angels - or stay out of it.
The characters in DxD would be quite shocked at first. Ichigo's appearance and his powers are so different from what they are used to. For example, Rias Gremory would probably be intrigued by Ichigo. She might try to form an alliance with him, seeing his potential as a powerful ally. Issei, being the main character in DxD, would likely be both jealous and in awe of Ichigo's abilities, and might challenge him at first but then learn from him over time.