Lune (ルーネ), from the eroge Himekishi Olivia (姫騎士オリヴィア). Trained on game cg rather than the OVA. Will be censored so tag as needed. Adding "no helmet,no armor" to the positive and "valkyrie,helmet,armor" to the negative prompt might be necessary to avoid having the armor appear. Cute valkyrie is cute too.
Prompt
lunehimek,very long hair,blonde hair,blunt bangs,red eyes,single braid