school was successful since I relied 100% on your support. For FINeSSE, you taught me everything step by step because I didn't know anything. For Lorentz violation, even though it was a spin-off subject for me and you, but you were so generous, supportive, and patient.And for MiniBooNE, the CCQE work couldn't have been done without your ideas. I am really proud of the amount of work I present in this thesis; it is the evidence of what a good work relationship we have. Finally I want to apologize for my bad English and for how you always had to correct it, including in this thesis. This acknowledgments section is the only one place in all my writings for which you didn't correct my English! Thank you Rex.My first three years were supported by the people in Indiana.I wish to give sincere appreciation to Chris Cox and Nikodem Pop lawski, I think it was my fate to see you from the very first day in US. I had a hard time (as you know), but because of your help, I not only survived, but also changed my style to be more suitable in this country. No one ever was so influential for me as Chris, I think. And Niko, before Thank you for sharing good times with me. I also want to thank Hans-Otto Mayer, Jack Doskow, and Gerard Visser for your help and inspiration for the work on FINeSSE. Thank you everyone.My friends from the classroom, it is a very strange feeling that now all we are going somewhere to do something, but we have known each other more than six years! Liliana Cabellero, you changed shy Teppei...to an emotional salsa dancer! If the dancing is my mother of energy, then Lily is founding mother of energetic Teppei. Muchas gracias. Leah Welty and Jason Rieger are the first real American students I met. When you described Chicago, I didn't understand very much, but now, yeah, I love this city and want to stay here more. Heechang Na, thank you for talking with me every time I stopped by your office, v because you are so kind and welcome and easy to talk with! Haiyang "Ocean" Yan, I am proud that I nicknamed you. I think you are a very good physicist. Thank you for teaching me a lot about Chinese history and physics. I always enjoyed it. Masaki (& Shizuka) Ishitsuka is the first Japanese fellow I met at Indiana even though I left Bloomington before you came. I always enjoyed talking about neutrinos with you, your view of physics is very unique and interesting to me. Thank you. Yun-Chan, Tony, George, Jay, Helber, Jorge, Shinya... I had so much fun in Indiana because of you. Thank you very much.One of the reasons I wanted to be a physicist is that physicists make friends all over the world so easily. I met many friends at conferences, summer schools, etc. Thank you to everyone who called me a crazy Japanese, even uploading my stupidities on YouTube.