1. Yukio begins by molding chakra inside his chest while converting it into water chakra. He spews the technique while simultaneously evaporating it into a large mist that surrounds both him and Choji, creatign a thick blanket of mist that covers the entire battle field. (Kirigakure No Jutsu - Hidding in Mist Jutsu)
After doing this, Yukio releases earth chakra through his feet into the earth underneath him, transforming it into fine sand, allowing him to dig through the ground and then appear behind Choji. (Doton: Moguragakure no Jutsu – Earth Release: Hiding like a mole technique)
After appearing behind the Akimichi, Yukio quickly equips himself with a kunai and stabs it into Choji's chest with a swift movement. Because of the speed of the attack, Choji would have almost no chance of defending against it. Choji's chance of being able to defend is also increased greatly by the thick mist and the fact that Yukio appeared behind him.(Muon Satsujin Jutsu - Silent Homicide Technique)
2. After seeing Lee start running towards him, Yukio quickly performs 4 handseals and releases lightning chakra from everywhere on his body, causing a bright blinding light to emanate from his body, blinding Lee. (Raigen Raikochu – Lightning Illusion Flash of Lightning Pillar)
After Lee is blinded, Yukio flows lightning chakra through the blade of his sword after unsheathing it, causing the light to disappear. (Kusanagi no Tsurugi: Chidorigatana) - Grass Cutter Sword: One Thousand Birds Katana
Then, with a swift and silent swing of his sword, Yukio slashes at Lee's head, decapitating him. (Muon Satsujin Jutsu) - Silent Homicide Technique)
3. I think it is very useful because it allows you to kill the opponent quickly without alerting them of your presence.
4. Even though it can be used to kill the opponent, it might not be very effective if you do not use it to strike a vital area. Also it is D-rank so it is not that powerful.
5. To stop the opponent from striking, I would use a quick jutsu to release chakra from my body and repel them such as (Raiton: Chidori Nagashi) - Lightning Release: One Thousand Birds Current or (Jūkenpō: Ichigekimi) - Gentle Fist Style: One blow Body