One idea could be that the OC has a special power that only activates when in close proximity to Ichigo. For example, the OC can sense Hollows from a great distance, which helps Ichigo in his battles against them.
Show their interactions over time. Have them start as acquaintances, then friends, and slowly develop romantic feelings. For example, they could start by training together, sharing their experiences about the spirit world.
There's 'Soulmate's Journey' which is a really popular one. It delves into the idea that they are soulmates in a more spiritual and emotional sense. It has some really touching moments that show their love and loyalty to each other. It also includes some great action scenes that are true to the Bleach universe.
In lemon fanfiction, Ichigo Kurosaki might be depicted with a different personality. Sometimes, authors explore his more emotional and vulnerable sides that might not be as prominent in the original work. For example, he could be shown in a romantic relationship where his protective nature is emphasized in a new way.
One appeal is that it gives fans a chance to see Ichigo in new and unexpected situations. Since lemon fanfiction often involves romantic or steamy elements, it can show a different side of his character that we don't usually get to see in the main series.
One interesting story could be where Ichigo and Yachiru go on an adventure in the Soul Society together. They might encounter some strange spirits and have to use their combined skills to defeat them. Ichigo's determination and Yachiru's energetic nature would make for a great dynamic during the adventure.
The potential for different storylines is a big factor. In the anime/manga, their relationship was left with some room for interpretation. Fanfiction writers can take this and create all kinds of scenarios, like alternate universes where they are from different social classes or have different powers. This allows for a lot of creativity and exploration of their characters.
One common theme is the power dynamic. Since Ichigo is a powerful Soul Reaper, there could be stories where he protects the reader from Hollows or other threats. Another theme is the discovery of the reader's own hidden powers, with Ichigo guiding them. For example, the reader might be a new Soul Reaper in training.
One interesting plot could be a story where the reader has some sort of special power that Ichigo discovers. He then tries to help the reader control it while they also face various Hollow threats together. This creates a bond between them that goes beyond the normal hero - sidekick relationship.
First, understand the character of Ichigo Kurosaki. Know his personality traits like his determination, his sense of justice, and his protectiveness. Then, create a believable scenario for the reader character to interact with him. For example, if the reader is a new Soul Reaper trainee, how would Ichigo react? Also, focus on the relationship development. Don't rush into things. Let it grow gradually as they face challenges together.