Keiryu sight fishing may not be the right terminology. What I mean is
fishing by sight rather than by feel. If you wait to feel the bite, you
are waiting too long.
I would highly recommend fishing by sight rather than by feel. There are two possibilities: fishing with a light tenkara line or fishing with a keiryu rig. Which to choose depends mostly on water depth.
For shallow water, up to perhaps knee deep, a size 2.5 tenkara line will provide sufficient weight to cast (for most rods). No added weight is needed if the water is up to about a foot deep. In depths from mid-calf to about knee deep, one or two #10 shot, up to perhaps one #6 shot should be sufficient.
The tenkara line will have some sag, and the slack caused
by the sag allows the fish to take the worm without feeling tension on
the line. When a fish takes, you will see the line tighten or move to the side. Immediately
tighten the line to set the hook.
This is the method I wrote about in the Ultralight Worm Fishing article. The photos show the TenkaraBum Tactical Nymphing Sighter but size 2.5 tenkara line will work as well.
For water over knee deep, you will probably need more weight, possibly one BB shot, and for that depth and weight, it is better to use a keiryu rig. I would suggest making a keiryu line in three sections. I would make the top section (called the tenjo line) from a light hi-vis line. Depending on the length of the rod, this section could be anywhere from 3' to 6' long. The middle section (the main portion of the line) should be tippet material with a breaking strength weaker than the top portion.The lowest section, to which you tie the hook and the split shot should be the lightest of the three sections (anywhere from 5X to 8X, depending on the size of fish you expect to catch). I would make the length of this section equal to the shallowest water you expect to fish. My Keiryu Lines article explains the keiryu rig in a bit more detail.
Tie three to four yarn markers around the main portion of the line so that the lowest one is above the surface when the split shot is just occasionally ticking the bottom. Watch the markers for indication of a strike or a snag.
For this rig, fishing across is better than fishing upstream.
Initially, you will not be able to tell if a dip in the markers is
caused by a fish or by a rock. If you then set the hook by pulling
the rod upstream, it will still hook a fish but will often dislodge the
hook or split shot from a rock, whereas setting the hook by pulling
the rod tip downstream can make a snag impossible to free. You can't
pull the line upstream to strike if the hook is upstream from where you are standing. (Fishing upstream is fine when using no weight in shallow water because the unweighted worm almost never gets snagged on rocks.)
With practice, you may be able to differentiate the sharper dip or twitch in the markers caused by a fish taking the bait from the slower change in the orientation of the markers caused by the hook or split shot hanging up on a rock or twig. For a snag, the markers will often change from angling upstream as shown in the photo above, to forming a slight "C" shape, to then angling downstream.
You will not have to strike sharply to set the hook. Just move the rod tip to tighten the line. It should be quick but not forceful.
For both rigs, but for the tenkara line rig in particular, you will
see strikes long before you feel them, and before the fish have a chance
to take the worm deep. With the keiryu rig, which is more vertical,
you will often feel the hit at the same time you see it - but not always
- if the fish takes the worm and goes to the side rather than down, you
may not feel a thing until it is much too late.
The reason keiryu rods have softer tips is to allow you to see the strike before the fish feels the tension. If you are waiting to feel the strike, you are giving up that advantage. When you feel the fish, it feels you! Either the fish will spit out the worm - which it really will do if the line is tight and it feels the tension on the line, or it will have had time to swallow the bait if the line had been slack. For keiryu, sight fishing is better than fishing by feel.