Raise the hand like shomen-uchi and attack directly - it is uke who moves off the line (although I know in some places tori moves off the line too - and we try it too sometimes - if tori has his posture up, for example, uke has to attack slightly around it - I think if you make the distinction then you are more aware - and as tori, I myself tend to have no-posture - arms by the side). A more important point is what tori does. What I insist on is that tori moves off the line slightly and then moves into uke directly - kind of like two separate movements - at first. So there is a sideways avoidance then a direct counter attack before moving into technique. I know that the more ususal method is to avoid, turn, and move in all in one go (for irimi) but for many people, the result is that they do too much turning and not enough moving in towards uke - if they did it with a sword in this manner the momentum of the sword swing would likely add spin to their taisabaki and they would lose control of their own movement. Anyway, after making use of two separate movements I find that students can make a better deal of the more usual - all-in-one movement.