It‘s unclear to me whether you’re looking for plants that bloom only in those months, or if you’re looking for something which has a bloom period that includes parts of those months.

Regardless, Pieris japonica, Aucuba japonica and Hamamelis japonica are three shrubs that meet your strict requirements, although the blooms on the Aucuba aren't particularly showy. Chaenomeles japonica is another possibility, though I think April blooms would be more likely. But you could get some late March blooms in z7 if the weather conditions were favorable.

with that early flowering period there are only bulb/ corm plants, like growing in woodlands or meadows, looking at it from a biological angle.

so you could search for "japanese bulbs" or something.

all other japanese perennials I know flower in summer or fall

chaenomeles, primula and hepaticas come to mind immediately (my chaenomeles has been in flower continuously since January...but it is a hybrid - either 'Crimson and Gold' or Rowallane)

Thanks guys I will look into those. My ume bloomed already and they’re done but they usually bloom in first week of April here. Some warm marches maybe last week of March. But I’m looking for a realiable feb-March bloomer.

O yeah, camellia. and chimonanthes (but that might be Chinese).

Witch hazel Hamamelis japonica has the species and a few named forms.

Mahonia japonica should bloom reliably in late winter. But other flowering shrubs can be much more easily influenced by weather conditions and their bloom time swing by weeks to a month or more in either direction. Plants do not follow a calendar so you cannot expect them to reliably produce flowers on a specific date.

I know you have mentioned these before lol.

https://link.springer.com/article/10.1007/s12225-011-9285-9

https://www.travelonthebrain.net/japan-spring-flowers/

I still can't find much online info on native spring bulbs and flowers of Japan, but their are usually Asian counterparts to our wildflowers. How is your peony doing after getting nibbled on? lol I'm trying to secure a golden lace plant that only 2 places carry and now I've noticed the punctiflora and want it badly too! I have my spring bulbs and ephemerals that bloom early in the spring. The bloodroot,Sanguinaria canadensis and Trilliums are blooming now, soon to be followed by the wild geraniums, Virginia bluebells and dutchman's breeches. I need to try some native Hepaticas again and stock up on spring anemones anemonellas.

https://www.greatdixter.co.uk/nursery-catalogue/products/patrinia-punctiflora/

The shipping costs???

Thanks for the links. My peonies are only growing from the shoots that were not nibbled and the ones that nibbled aren't growing at all. It just stopped there.

I just wanted a plant other than my petasites that has the ability to signal the start of spring. Last year my fiance took me to an arboretum for my birthday in late march and saw an enormous patch(scattered in many areas as well) of winter aconites just emerging from the melting snow and it was the best feeling ever. Not just because they were beautiful but the feeling of the end of the dreading winter and the onset of spring glory... nothing beats that. I guess I will go with adonis since they look a little similar in structure. I originally didn't want to because they look like they spread super slow and I didn't want just tiny spots of yellow in only a few places in my garden. I wanted like a mass groundcover but I'm ok with it now. I might try hepatica too. Hamamelis is also great but I don't know if I have room for such a large shrub. Sah67, as long as it is showing blooms in March at least I am fine with it. I don't want something though, however, that sometimes bloom in late march or sometimes in early april. Like what gardengal says with the mahonia and my ume tree does.

I just saw a lovely photo of hylomecon japonica used as a ground cover - very similar to winter aconite in flower color, and I believe meets the rest of your requirements.