Your jeans are made from raw, unsanforized Japanese selvedge denim. This means they have not been pre-washed and will shrink slightly on their first wash. This has been accounted for in your pattern.
Expect 3–5% shrinkage in length. This is normal and intentional.
Cold wash only, inside out, gentle cycle. Never hot water.
Hang dry only. Never tumble dry.
Wash as infrequently as possible. Spot clean where you can. Freezing your jeans overnight kills bacteria and odour without affecting the fabric or fade.
Raw denim will fade and crease uniquely to the way you wear them. This is the whole point — wear them hard and they'll become yours.